Adaptive hybrid wireless and wired process control system

ABSTRACT

A hybrid wired and wireless architecture for a process control system is disclosed that includes hierarchical adaptability and optimization capabilities. The system is arranged in three tiers, the first including a number of wireless end devices exchanging packets of data and/or instructions with the distributed control system, where each wireless end device is associated with one or more meters, remote terminal units, diagnostic devices, pumps, valves, sensors, or tank level measuring devices. The second tier includes a plurality of wireless routers, each including a memory that stores a routing table and a processor that routes packets. The third tier includes a master wireless gateway device operably connected to receive packets from and transmit packets to the distributed control system. The processor of each of the wireless routers routes packets across the tiers between the end devices and the wireless gateway devices based on the stored routing table.

RELATED APPLICATIONS

This application claims priority to and is a divisional of U.S. patentapplication Ser. No. 12/938,432 filed on 3 Nov. 2010, which in turnclaims priority to and is a continuation-in-part of U.S. patentapplication Ser. No. 12/990,588 filed on 1 Nov. 2010, which in turnclaims priority to international application PCT/US2009/042517 filed on1 May 2009, which in turn claims priority to U.S. Provisional PatentApplication No. 61/049,682 filed 1 May 2008. The entirety of each citeddisclosure is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to process control systems and methods,and more particularly to such systems and methods that includehierarchical adaptability and optimization capabilities to operate ahybrid wired and wireless process control and/or automation networkwhile utilizing minimum system resources.

2. Description of Related Art

The current architecture of the wireless networks in various commercialand industrial processing facilities, including hydrocarbon andpetrochemical plants, necessitates that most information packetstransmitted from the wireless end devices (WEDs) have a singledestination, the Central Control Room (CCR). However, the transmissionsfrom the WEDs are passed through several wireless intermediate devices(WIDs) and wireless gateway devices (WGDs), resulting in multiple copiesof the same packet arriving at the Central Control Room (CCR)gateway(s). WEDs can transmit to and receive from all other devices, butcannot route to other devices. WIDs transmit to and receive from allother devices, and route to other devices. WGDs transmit to, receivefrom, and route between other devices, and also conduct high levelapplications including protocol translation and assignment of paths forsource-destination pairs. As used herein, the components WEDs, WIDs andWGDs are also referred to as “nodes.”

Since a typical industrial process requires thousands of instruments,e.g., sensors, valves, diagnostic devices, and the like, that all musttransmit information to the CCR, there exists, in the present state ofthe art, massive contention for access over the wireless bandwidthspectrum in and around the CCR. This contention ultimately results indegradation of the signal throughput and high packet loss rate.

As used herein, “commercial and industrial processing facilities”include chemical plants, hydrocarbon facilities, petrochemicalfacilities, manufacturing factories, or any facility that uses wirelessprocess automation and/or control.

FIG. 1 is a schematic diagram of hardware interconnectivity for atypical prior art process control network 500 in a commercial and/orindustrial processing facility. In FIG. 1, wired connectivity isdepicted with solid double-arrow lines between nodes, and wirelessconnectivity is depicted with dashed double-arrow lines between nodes.Several junction boxes 506 (JBs), and up to several hundred in typicalprocess control systems, are connected, typically by copper or fiberoptic wires, to one or more marshalling cabinets 504 in the centralcontrol room 501 (CCR). The CCR 501 includes a distributed controlsystem 502 that generally includes at least one processor coupled to amemory for providing functionality necessary for plant automation and/orcontrol. Junction boxes 506 provide data distribution functionality andpower (current and voltage) control, and are equipped with requisitepower connectivity and a suitable environmental enclosure. Themarshalling cabinets 504 provide interconnectivity between severaljunction boxes 506, and serve as an access point in the CCR 501 forinstallation of additional JBs, maintenance, testing and service. TheJBs can be connected to any wired communication enabled pressure sensor,temperature sensor, pump, valve, tank level gauge, and the like.Typically these end devices can be the same process control device thatconnects to a WED, the difference being the I/O card of the end device.That is, end devices can be connected to the JBs when they supportwired-only connectivity, or both wireless and wired connectivity. Forend devices that support wireless-only connectively, a WED must be used.Typically, spare copper or fiber optic wires are provided in a trenchbetween each junction box 506 and the CCR for future growth andexpansion. These wire connections can be accessed at the junction boxes506 and/or surrounding areas. The junction boxes 506 and the planthardware in wired communication thereto (not shown), along with themarshalling cabinets, for, an independent wired network 509 in typicalcommercial and industrial processing facilities.

Traditionally, plant and industrial networks have relied on the wire asa means for communications and networking. Wireless communications wereintroduced within facilities as independent networks. Thereforecommercial and industrial processing facilities commonly include awireless network that is independent of the wired network. The wirelessnetwork generally includes a master WGD 510 coupled to the distributedcontrol system 502 via an input/output interface 508. Several WGDs 512and WIDs 514 are interconnected to each other and to the master WGD 510.The WIDs 514 receive and transmit data from/to the WEDs 516.

In prior art systems as shown in FIG. 1, the wireless network 520 underthe control of the master WGD 510 Gateway is completely isolated fromthe wired network 509 connecting the several junction boxes 506 throughthe marshalling cabinets 504.

All field devices and subsystems, in the order of thousands, aretypically within a relatively small area in a commercial and industrialprocessing facility, e.g., in a space on the order of about 500 metersby about 300 Meters. The WEDs 516 at the field devices generallybroadcast their data, which is received by any and all available WIDs514 and/or WGDs 512. The WIDs 514 retransmit the data to WGDs 512 andthe master WGD 510, and the WGDs 512 retransmit the data to the masterWGD 510. Ultimately, packet selection is accomplished with one or moreappropriate software and/or firmware modules executable by the masterWGD 510, which select the first packet that appears to have accuratedata, and subsequent packets containing copes of the same data arediscarded. This architecture, with substantial redundancy, isconventionally implemented to ensure that all of the data transmittedfrom the WEDs 516 is received at the CCR 501 for subsequent actionand/or data collection purposes.

The International Society of Automation (ISA) has established a WirelessSystems for Automation Standards Committee (ISA-SP100) tasked withdefining wireless connectivity standards. The SP100 wireless standardfor process automation systems is applicable to industries such as oiland gas, petrochemical, water/wastewater treatment and manufacturing.The SP100 standard is intended for use in the 2.4 GHz band, with datatransfer at speeds up to 250 kilobytes per second within a 300 meterrange. SP100 devices have relatively lower data rates and energyrequirements than comparable wireless Local Area Networks (LAN), as theyare intended to be low-cost devices. Another commonly employed wirelessprocess control and/or automation network has been recently developed asa derivative of the Highway Addressable Remote Transmitter (HART)Communication Foundation protocols, referred to generally as the HART®protocol.

The SP100 protocol specifies different types of communications,categorized as “usage classes,” and increasing in criticality based upondecreasing numerical designation. “Class 0” communications include thosecategorized as critical for safety applications such as emergencyshut-down systems, and are deemed always critical; “Class 1” is forclosed-loop regulatory control, often deemed critical; “Class 2” is forclosed-loop supervisory control, usually non-critical; “Class 3” is foropen-loop control; “Class 4” is for alerting or annunciation; and “Class5” is for data logging. Certain events, such as alarms, can havedifferent classifications of service depending on the message type.

FIG. 2 is a schematic diagram of a prior art architecture for a wirelessprocess control system 600 of the prior art, e.g., operating under theSP100 standard. In general, devices in an SP100 system are divided intothree categories, commonly referred to as “tiers.” Tier 1 includes enddevices, such as meters, remote terminal units, valves, sensors, tanklevel measuring devices, and the like, each of which is connected to aWED 616. Tier 2 includes WIDs 614 and tier 3 includes WGDs 612. Asdescribed above, WEDs 616 can transmit to and receive from all otherdevices, but cannot route to other devices; WIDs 614 transmit to andreceive from all other devices, and route to other devices; and WGDs 612transmit to, receive from, and route between other devices, and alsoconduct high level applications including protocol translation andassignment of paths for source-destination pairs. In addition, a masterwireless gateway device 610 is provided at tier 3, which is coupled tothe CCR 601 and controls the ultimate communication of data to and fromthe DCS 602. Individual nodes are also labeled for further clarity ofdescription and to simplify certain examples provided herein.

Connectivity between WEDs L17 and L13 and WGDs L35 and L31,respectively, is illustrated, although as will be understood by one ofordinary skill in the art, connectivity is typically provided betweenall WEDs 616 and the master WGD 610 for communication with the DCS 602.A path is the series of nodes commencing with the transmitting node,ending with the receiving node, and including the routing nodestherebetween. A link is a specific coupling within such a path. Forexample, L17-L293-L292-L36-L35 is a path for the source-destination pairL17-L35, and L292-L36 is one of the links within this path.

Devices in an SP100 wireless system are generally connected in the formof a mesh or star-mesh network. Connection between the various devicesis performed through radio communications, for instance as specified bya Carrier Sense Multiple Access with Collision Avoidance (CSMA-CA)protocol or the like, and connections are established at a network layerand a Medium Access Control (MAC) layer.

In existing wireless process control and/or automation systems, everyframe transmitted from a WED 616 to the DCS 602 at the CCR 601 istreated the same, regardless of its usage class or criticality. Thestandards mandate that the transmitted frames reach the DCS 602 within aspecified maximum allowable end-to-end time delay and a specified frameerror rate (FER). Commonly, all WIDs 614 and WGDs 612 route incomingtraffic irrespective of the usage class, and without regard to a frame'sstatus as an original transmission or a retransmission. Multiple pathsbetween WEDs 616 and the master WGD 610 are typically specified in arouting table for increased reliability of data frame transmission andreceipt. Retransmission of frames occurs and is requested if thereceived frame is judged to be erroneous or no acknowledgment isreceived (i.e., a timeout occurs).

While a large number of paths provide a certain degree of reliability,this topology increases the bandwidth requirements for the wirelessspectrum and battery energy usage, and the quantity and/orsophistication level of the requisite hardware. Redundancy oftransmission paths also requires additional capital investment inhardware and increased costs for the necessary testing and maintenanceof the additional routers. In addition, channel contention often occursdue to high channel utilization, increased latency between the WEDs 616and CCR 601, and frame blocking. Therefore, diminishing returns result,such that an increase in the number of paths beyond a certain level willnot significantly increase the reliability, thereby inefficiently usingbandwidth, hardware and battery power. Wireless implementation of theSP100 and the HART® protocols have suffered similar drawbacks includingexcess battery usage and increased channel contention.

Therefore, there is a significant need to reduce the number ofunnecessary transmissions and reduce the number of wireless routers. Inaddition, a need exists for reliable and adaptable methods and systemsto operate a wireless process control and/or automation network whileutilizing minimum system resources.

Accordingly, it is an object of the present invention to reduce theoverall congestion of wireless traffic in and around the CCR.

It is another object of the present invention to transmit, from one tierto another, data packets that meet optimal performance requirements foreach source-destination pair, and maximize the quality of transmittedpackets for each source-destination pair.

SUMMARY OF THE INVENTION

The above objects and further advantages are provided by the method andsystem of the present invention for improving communications within acommercial and industrial processing facility. In one aspect, the methodand system provides hierarchical adaptability components to a processcontrol and/or automation network that increase system efficiency andreliability. The invention comprehends an intelligent and efficientprocess to design and operate a process control and/or automationnetwork while utilizing minimum system resources. In certainembodiments, path requirements are specified per usage class wherebyminimum utilization of bandwidth, paths and hardware is allocated whilemeeting plant environment requirements for services such as closed-loopregulatory and supervisory control, open-loop control, alerting, loggingand remote monitoring.

In wireless systems having a large number of networked devices,efficient spectrum usage and delay minimizations are critical design andplanning factors. Wireless process control and/or automation networks,including those operating under the ISA-SP100 protocol and/or thewireless HART® protocol, co-exist with other wireless systems operatingin similar bands, e.g., 2.4 MHz, such as wireless LAN (including IEEE802.11), BLUETOOTH™, ZIGBEE™, and the like. Efficient spectrumutilization in operation of a wireless process control and/or automationnetwork in turn benefits other wireless systems utilizing the samefrequency band. Accordingly, the present invention minimizes spectrumutilization by routing only frames and/or packets that meet one or moreconstraints. Paths are identified that meet the specified constraint(s).During operation, paths are discarded and/or replaced when they nolonger satisfy the constraint(s).

In addition, wireless process control and/or automation networks arecommonly deployed in harsh and classified areas, such as hazardous areasreferred to as “Class 1, Division 1” and “Class 1, Division 2.” In theselocations, flammable gas mixtures can be present. Many wireless controland/or automation devices in these environments are battery-operated,mandating periodic battery replacement. Accordingly, reducing batterydemand through the use of more efficient spectrum utilization results inhigher battery lifecycle, lower capital and operating costs, and reducedoccurrences of worker access to these network devices in areasclassified as hazardous.

In one method of operating a wireless process control and/or automationnetwork according to the present invention, steps are carried out toselect a minimum number of paths for one or more source-destinationpairs. Potential paths between each source-destination pair areinitially chosen. The reliabilities of each of the potential pathsand/or the effective reliabilities of groups of paths are determined.Paths or groups of paths that meet the minimum reliability requirementsare identified by comparing the calculated reliabilities and/oreffective reliabilities with minimum reliability requirements specifiedin a set of routing rules. Paths are selected from the identifiedreliable paths based on a minimum number of paths specified in the setof routing rules and assigned in a routing table. Paths or groups ofpaths above the specified minimum number of paths that meet thereliability requirements are discarded, i.e., not assigned in therouting table (as opposed to disabling the path), or assigned asalternate paths in the routing table. The paths that are discarded canbe assigned in the future, for instance, if one of the previouslyassigned paths or alternate paths encounters excessive traffic and canno longer meet the requisite constraint(s) including the minimumreliability requirements.

In another method of operating a wireless process control and/orautomation network according to the present invention, steps are carriedout to select paths based on constraints related to end-to-end delaysbetween a source-destination pair.

In a further method of operating a wireless process control and/orautomation network according to the present invention, steps are carriedout to select paths based on constraints related to tier delays forlinks within a given tier. Notably, employing a constraint based on tierdelays minimizes the number of links or hops in a given path between asource-destination pair.

In an additional method of operating a wireless process control and/orautomation network according to the present invention, steps are carriedout to select a minimum number of reliable paths that further meetconstraints related to end-to-end delays and/or tier delays.

In still another method of operating a wireless process control and/orautomation network according to the present invention, steps are carriedout to select a minimum number of reliable paths that further meetconstraints related to one or more of end-to-end delays and/or tierdelays, maximum throughput per link, and a minimal number of hops.

In one system of the invention for operating a wireless process controland/or automation network, a route optimization module is executed byhardware which can include one or more of the wireless gateway devices,a separate computing device in communication with the wireless network,or a combination thereof. The route optimization module includes a pathdetermination sub-module that determines possible paths between theselected source-destination pair. A reliability calculation sub-moduleis provided that determines the reliability of each of the possiblepaths, and/or the effective reliability of one or more groups of paths.The route optimization module also includes a reliable pathidentification sub-module that identifies reliable paths or groups ofpaths by comparing the reliability and/or effective reliability withminimum reliability requirements specified in a set of routing rules,and a path assignment sub-module for assigning reliable paths or one ormore groups of paths to a routing table based on a minimum number ofpaths specified in the set of routing rules. Paths or groups of pathsabove the specified minimum number of paths that meet the reliabilityrequirements are discarded, i.e., not assigned in the routing table, orassigned as alternate paths in the routing table.

In another system of the invention for operating a wireless processcontrol and/or automation network, an end-to-end delay minimizationmodule is provided, in which paths are selected based on constraintsrelated to end-to-end delays for paths between a source-destinationpair.

In a further system of the invention for operating a wireless processcontrol and/or automation network, a tier delay minimization module isprovided, in which paths are selected based on constraints related totier delays for links within a given tier.

In an additional system of the invention for operating a wirelessprocess control and/or automation network, a delay minimization moduleis provided, in which paths are selected based on constraints related toboth end-to-end delays and tier delays.

In still another system of the invention for operating a wirelessprocess control and/or automation network, a module is provided toselect a minimum number of reliable paths, and one or more additional orsub-modules to select paths based on further constraints related toend-to-end delays and/or tier delays, maximum throughput per link, aminimal number of hops, or a combination of one or more of end-to-enddelays and/or tier delays, maximum throughput per link, and a minimalnumber of hops.

In certain embodiments, the reliability, e.g., the maximum allowableframe error rate (FER), is specified for one or more of the usageclasses, and the assigned minimum number of reliable paths is specifiedper usage class. Usage classes or groups of usage classes with higherdegrees of criticality, e.g., classes 0 and 1 in an SP100 system, have ahigher reliability threshold, i.e., lower maximum allowable frame errorrates as compared to usage classes of lower criticality. Further, usageclasses of lower criticality can have fewer assigned minimum reliablepaths.

Further embodiments of the process of the present invention provide thatthe maximum allowable frame error rate per usage class, the processcontrol wireless traffic distribution, the links' reliability profile,tier delay, or a combination of these factors are used to generate asubset of paths containing a minimum number of paths with associatedreliability weight. For source-destination pairs in which the minimumnumber of paths is not attained based on the above-described routingassignment process or the above-described sub-modules, selective pathsare combined, i.e., groups of paths, or additional paths areincorporated, until the end-to-end frame error rate for each usage classis lower than the class's maximum allowable threshold, while applyingthe criteria of employing a minimum number of intermediate links.

Embodiments of the present invention include additional steps orsub-modules for incorporation within conventional wireless networkprotocols, including: (1) defining a maximum allowable delay for eachtier; (2) including usage class bits to the routing table; (3)considering whether a frame is a retransmit frame; (4) providing anaction-type bit to the frame format structure where the received framesfor a destination are not actioned until the end of the maximumallowable delay (i.e., the received frame is not actioned until the endof the maximum allowable delay to ensure that all frames arriving fromdifferent routes are received and the frames with a high qualityindicator are passed to the CCR for action); (5) dropping and/or routingthe frame as a function of the usage class; and/or (6) during abnormalchannel conditions, sending a control message to WIDs and/or WGDs in awireless process control and/or automation protocol network to allowrouting of frames for a particular pair of source-destination pairsirrespective of the usage class, thereby dynamically increasing thenumber of available paths. Accordingly, in certain embodiments, themethod and system of the present invention minimizes the required numberof frames transported over wireless links while meeting reliability andlatency requirements.

In an example described below, it is demonstrated that by using thesystem and method of the present invention in a wireless SP100 network,(1) the battery lifecycle of hardware is extended by more than 60%; (2)the cost of an SP100 system is significantly reduced due to reduction inthe required number of WIDs and WGDs; and (3) spectrum utilization isreduced by at least 55%. These benefits are accomplished whilemaintaining the design requirements for plant applications such asclosed-loop regulatory and supervisory control, open-loop control,alerting, and remote monitoring/logging.

In still further embodiments of the present invention, a new hybridwired and wireless architecture is deployed for process control and/orautomation. The new architecture includes several field network sets(FNSs). One or more FNSs in the intermediate tier each include one ormore of a WID, a modified WID (MWID), and a set of a MWID coupled with ajunction box (MWID-JB). One or more FNSs in the gateway tier includesone or more of a WGD, a modified WGD (MWGD) and a set of a MWGD and a JB(MWGD-JB). The master WGD may alternatively be a master MWGD or masterMWGD-JB, with a MWGD-JB being preferred over a MWGD as the masterdevice, and a MWGD being preferred over a WGD as the master device. EachFNS includes an anchor packet selection device. This hybrid systemincludes path selection and optimization with frame selection, packetselection and routing through a predetermined number paths depending onthe class of service. Thus, the routers and gateway devices of each FNSact as a single device to route data to routers and gateway devicesexternal to the FNS. The combination of these features is used toenhance the system reliability and performance. An FNS may also span twotiers, such as an FNS that spans tier 2 and tier 3.

In another embodiment, an FNS can have a secondary anchor packetselection device, for example, to provide redundancy, or in order tocarry more traffic load where one device is inadequate due to packetload.

The architecture of the present invention improves performance andreliability of a process control and/or automation network by:

minimizing the required number of unnecessary transmission of packets,

minimizing spectrum congestion and improving spectrum utilization,

minimizing the hardware required to support a plant wireless systemunder certain mandated requirements,

maximizing the utilization of existing plant infrastructure, and

significantly increasing the battery life of wireless devices.

In addition, the total number of wireless routers can be reduced, and incertain embodiments, tier 3 gateway devices (except for the master WGD)can be reduced or eliminated altogether. This advantageously allows thenumber of data transmission to the CCR to be minimized, the spectrumusage to be maximized, packet loss to be reduced, and requisite hardware(and associated labor involved in deploying and maintaining suchhardware) to be minimized.

In conventional wireless automation and/or control systems, packetselection is accomplished at the master WGD by selecting the firstpacket with correct received information and discarding the subsequentreceived copies of the same packet. According to the present invention,however, packets are not progressed to the next tier until: (1) thenumber of packets required to meet the minimum performance requirementsfor each pair of source-destination is optimized (minimum), and (2) thequality of transmitted packets for each source-destination pair is thehighest.

According to one embodiment of the present invention, a plant wirelesssystem or a wireless process control network includes MWIDs or MWGDsthat perform (1) a selecting function, (2) a routing function, and (3)interface to a JB in the field network set via wired connection andneighboring WIDs via wireless connection. The routing function keepstrack of all MWID-JB sets, the MWGD-JBs, and the master WGD/MWGD, andadjust the routing dynamically (per packet) as needed.

According to another embodiment of the present invention, a plantwireless system or a wireless process control system includes MWIDs andMWID-JBs grouped into FNSs. The MWIDs and MWID-JBs within each set areeither hardwired or connected via a junction box router, while WIDs arewirelessly connected to MWID-JB or MWIDs. Each FNS can be connected tothe CCR directly (through existing wiring available via the JB),connected wirelessly to intermediate MWGD-JB, or connected wirelessly tothe master WGD/MWGD. Accordingly, each FNS can have single MWID-JBtasked with routing traffic to the destination.

According to another embodiment of the present invention, a plantwireless system or a wireless process control system includes, e.g., fora particular source-destination pair, one particular MWID within a FNSthat is tagged as an anchor point for receiving all packets from thatparticular source, selecting the one packet with the highest qualityindex, and forwarding that one selected packet toward the destination(CCR) through MWID-JB, possibly in multiple paths. In the reversedirection, the anchor MWID within a set for a particularsource-destination pair receives the packet from the CCR and transmitsit ultimately to the WED. If packets belonging to particularsource-destination pair passes through two different MWID-JBs belongingto different FNSs, then each MWID-JB set will have an anchor packetselection MWID for that pair (i.e., a total of two MWIDs are required).If packets belonging to a particular source-destination pair passesthrough three different MWID-JBs, then each FNS will have an anchorselection by assigning a MWID for that pair (a total of three MWIDs arerequired). Executing the algorithms described herein determine if one ormore FNSs are needed for a particular source destination pair. Theanchor MWID within an FNS is needed to provide the packet selection fora particular source-destination pair, while the MWID-JB within the sameFNS is required to interface and route traffic to/from the CCR or masterWGD/MWGD. At the WGD tier level, the anchor MWGD within a set is used toprovide the packet selection for a particular source-destination pair,while the MWGD-JB within the same FNS is used to interface and routetraffic to/from the CCR or master MWG/MWGD. However, if a MWID-JB set isdirectly hardwired to the master MWGD, then the anchor selection in theWIGD tier will be (by default) the master MWGD.

According to a further embodiment of the present invention, a wirelessprocess control system includes a master MWGD that maintains theconfiguration of the sets, including which MWID-JBs belong to which set,which MWID-JB is the interface to the CCR and which MWID-JB is thebackup (if any). While a selected path for a particularsource-destination pair can vary from one transmission to another, theanchor packet selection device within a set for that particular sourceand destination pair remains the same until changed by an operator or ifcertain conditions arise (e.g., device failure, additional devices addedor the like) that result in re-designation of the anchor packetselection device. Source-destination pairs sharing one particular FNSwill distribute the selection function (load balanced) across the MWIDswithin that set.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofpreferred embodiments of the invention will be best understood when readin conjunction with the attached drawings. For the purpose ofillustrating the invention, there are shown in the drawings embodimentswhich are presently preferred. It should be understood, however, thatthe invention is not limited to the precise arrangements andinstrumentalities shown. In the drawings the same numeral is used torefer to the same or similar elements or steps, in which:

FIG. 1 is a schematic diagram of a process control and/or automationnetwork of the prior art including a wireless facility network and awired facility network that are distinct and not integrated except atthe CCR;

FIG. 2 is a schematic diagram of a wireless process control and/orautomation network of the prior art;

FIG. 3 is a schematic diagram of a wireless process control and/orautomation network in accordance with the present invention;

FIG. 4 is a schematic diagram of a hybrid wired and wireless processcontrol and/or automation network in accordance with the presentinvention;

FIG. 4A is a schematic diagram of a hybrid wired and wireless processcontrol and/or automation network in accordance with the presentinvention;

FIG. 5 is a schematic diagram of a hybrid wired and wireless processcontrol and/or automation network in accordance with the presentinvention;

FIG. 6 is a schematic diagram of architecture of a wireless processcontrol and/or automation network according to certain embodiments ofthe present invention;

FIG. 7 is a block diagram of a wireless end device according to certainembodiments of the present invention;

FIG. 8A is a block diagram of a wireless gateway device and a modifiedwireless gateway device according to certain embodiments of the presentinvention;

FIG. 8B is a block diagram of a wireless gateway device and a modifiedwireless gateway device according to certain embodiments of the presentinvention;

FIG. 9A is a block diagram of a wireless gateway device and a modifiedwireless gateway device according to certain embodiments of the presentinvention;

FIG. 9B is a block diagram of a wireless gateway device and a modifiedwireless gateway device according to certain embodiments of the presentinvention;

FIG. 10 is a block diagram of a junction box router according to certainembodiments of the present invention;

FIG. 11 is a block diagram of a basic computing device configuration inaccordance with embodiments of the present invention;

FIG. 12 is an overview of an example of the requisite number of pathsper usage class according to the present invention;

FIG. 13 is a block diagram of the optimization framework carried out byone or more modules in accordance with certain embodiments of thepresent invention;

FIG. 14A is a schematic block diagram including a route optimizationmodule in accordance with an embodiment of the present invention;

FIG. 14B is a flow chart of a method of assigning reliable paths for asource-destination pair in accordance with the present invention;

FIG. 14C is a flow chart of a method of assigning reliable paths for asource-destination pair in a hybrid network including field network setsin accordance with the present invention;

FIG. 14D is an exemplary routing table that can be created using themethod of FIG. 14C;

FIG. 15A is a schematic block diagram including an end-to-end delayminimization module in accordance with an embodiment of the presentinvention;

FIG. 15B is a flow chart of a method of assigning paths for operatingthe end-to-end delay minimization module in accordance with the presentinvention;

FIG. 15C is a flow chart of a method of assigning paths for operatingthe end-to-end delay minimization module in a hybrid network includingfield network sets in accordance with the present invention;

FIG. 15D is a detail of a path routing table to be used in a method ofassigning paths for operating the end-to-end delay minimization modulein a hybrid network including field network sets in accordance with thepresent invention;

FIG. 16A is a schematic block diagram including a tier delayminimization module in accordance with an embodiment of the presentinvention;

FIG. 16B is a flow chart of a method of assigning paths for operatingthe tier delay minimization module in accordance with the presentinvention;

FIG. 16C is a flow chart of a method of assigning paths for operatingthe tier delay minimization module in a hybrid network including fieldnetwork sets in accordance with the present invention;

FIG. 17A is a schematic block diagram including a delay minimizationmodule in accordance with an embodiment of the present invention;

FIG. 17B is a flow chart of a method of assigning paths for operatingthe delay minimization module in accordance with the present invention;

FIG. 17C is a flow chart of a method of assigning paths for operatingthe delay minimization module in a hybrid network including fieldnetwork sets in accordance with the present invention;

FIG. 18 is a flow chart of an overview of a method of defining fieldnetwork sets and assigning paths for source-destination pairs per usageclass;

FIG. 19 is a schematic diagram of a portion of a wireless processcontrol and/or automation network architecture depicting a set ofsource-destination pair components;

FIG. 20A is a chart of normalized power usage comparison for wirelessintermediate devices using the system and method of the presentinvention compared to prior art methods;

FIG. 20B is a chart of normalized power usage comparison for wirelessend devices and wireless gateway devices using the system and method ofthe present invention compared to methods of the prior art; and

FIG. 21A is a schematic diagram of a portion of a hybrid wired/wirelessprocess control and/or automation network architecture depicting a setof source-destination pair components and associated field network setsaccording to certain embodiments of the present invention; and

FIG. 21B is a schematic diagram of a portion of a hybrid wired/wirelessprocess control and/or automation network architecture depicting a setof source-destination pair components and associated field network setsaccording to certain embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3 is a diagram of a wireless process control and/or automationnetwork 700 such as one following the ISA-SP100 protocol; for clarity,only connectivity for WEDs L17 and L13 to WGDs L35 and L31,respectively, is illustrated. The path L17-L293-L292-L36-L35 is one ofthe paths of the source-destination pair of L17 and the CCR 701. Thecombination L292-L35 is considered one of the links within this path.The path L17-L291-L28-L34-L35 is a path independent fromL17-L293-L292-L36-L35, since no single intermediate link is common tothe two paths. Elements L11 through L17 are WEDs 716 at tier 1; elementsL21 through L29 and L291 through L293 are WIDs 714 at tier 2; andelements L32 through L36 are WGDs 712 at tier 3. In general, WEDs 716broadcast in all directions, however, for simplicity in the descriptionof the present invention, communication is depicted only between selectWEDs and WIDs. In network 700, the WGD L31 at the CCR 701 is the masterWGD 710, and the other WGDs L32 through L36 are additional WGDs 712 thatprovide additional links and/or serve as backup gateway devices in theevent that the master WGD 710 fails. In accordance with the presentinvention, a computing device 80 is provided that executes one or moremodules for path selection. These modules can be the route optimizationmodule 110, the end-to-end delay minimization module 210, the tier delayminimization module 310, the delay minimization module 410, othermodules that apply constraints including one or more of throughput andnumber of hops, or a combination including at least one of the foregoingmodules, to create the routing table 190 for path selection. Theresulting routing table 190 is loaded in memory of the routing WIDs andWGDs. The computing device 80 can be provided within or associated withthe master WGD 710, and/or within or associated with the DCS 702. Notethat some or all of the modules executed by the computing device 80 canbe executed in separate computing devices, e.g., certain modules at orassociated with the master WGD, other WGDs, WIDs, MWIDs and/or MWGDs.

As used herein, the term “routing table” refers to a collection of dataor instructions that specifies one or more paths between asource-destination pair, and can be in the form of a table, database,dataset or other collection of electronically stored data that includessuch instructions in a form that is readable by WGDs, MWGDs, WIDs and/orMWGDs in the present invention.

FIG. 4 is a diagram of a hybrid wired and wireless process controland/or automation network 800 according to the present invention. Thewireless connectivity is in accordance with a suitable process controlstandard, such as the ISA-SP100 protocol. As in FIG. 3, onlyconnectivity for WEDs L17 and L13 to WGDs L35 and L31, respectively, isillustrated for clarity. In FIG. 4, wired connectivity is depicted withsolid double-arrow lines between nodes, and wireless connectivity isdepicted with dashed double-arrow lines between nodes.

The plant architecture according to the present invention includes aplurality of field networks sets 820 (FNSs) in communication with theCCR 801 and/or a master WGD 810. The CCR 801 includes the DCS 802. Thecomputing device 80 can be provided within or associated with the masterWGD 810, and/or within or associated with the DCS 802. Each FNS 820 atthe intermediate tier (tier 2) includes one or more WIDs 814, one ormore modified wireless intermediate devices 815 (MWIDs), or acombination thereof. Furthermore, the FNS 820 e in tier 3 includesmodified WGDs 813 (MWGDs) and a JB 806. Note that one or more WGDs canalso be provided (not shown) in tier 3.

MWIDs or MWGDs within an FNS are employed to interface with a JB and/orto execute packet selection as described further herein. In a preferredembodiment, at least one MWID or MWGD is provided in each FNS 820 forconnection to the CCR 801 and/or the next tier. One or more additionalMWIDs/MWGDs can optionally be provided in an FNS 820 as backup, forconnection to multiple JBs in an FNS 820, and/or to co-execute packetselection module(s). Note that even if a MWID/MWGD is provided that doesnot serve as the node which connects to the JB and/or executes packetselection, these MWIDs/MWGDs perform all of the functionalities of aconventional WID/WGD. Determination as to installation of MWIDs/MWGDs asdevices at locations that that do not execute packet selection module(s)and/or include wired connectivity can be made based on factors includingbut not limited to capital cost, whether the installation is an upgradeor a grass roots installation of a control/automation system, theanticipated need to define further network sets during futuremodifications or additions, and any requirements for availability ofbackup modified WIDs/WGDs.

One or more MWIDs and/or MWGDs in the architecture of the presentinvention each contain stored in their respective memories one or morerouting tables to provide path selection, similar to the WIDs and/orWGDs described with respect to FIG. 3. In addition, one or more MWIDsand/or MWGDs in an FNS 820, particularly the MWID or MWGD selected asthe anchor device, executes a packet routing module. The packet routingmodule provides functionality to (1) route packets to correct JBs withinan FNS; (2) route packets to the correct anchor packet for a particularsource-destination pair; (3) route packets from one FNS to another, and(4) provide routing tables to assist in the wireless-wired networksintegration.

In general, WEDs 816 broadcast in all directions, however, forsimplicity in the description of the present invention, communication isdepicted only between select WEDs and WIDs/MWIDs. For example, accordingto the present invention, when a WED transmits in all directions, itwill reach several FNSs, each potentially having several MWIDs. Byapplying the routing table according to the present invention, apredetermined number of FNSs are required and selected (e.g., two), thusthe transmission is only routed through selected FNSs. Upon furtherapplication of the routing tables of the present invention, certainpaths of WIDs and/or MWIDs are selected within the predetermined numberof FNSs.

Certain FNSs 820 include one or more junction boxes (JBs) 806, e.g.,FNSs 820 a and 820 b. In addition, certain FNSs do not include JBs, inwhich the MWID or MWGD serves to execute the packet selection processaccording to the routing table. Communication to the next tier in theFNSs without JBs is accomplished by wireless connectivity.

In addition, certain embodiments of the FNSs 820 comprise at least oneset 805 including a MWID 815 coupled with a junction box 806, the setreferred to herein as a MWID-JB 805. For instance, one MWID-JB 805includes the set of the MWID L292 and its proximate JB 806; anotherMWID-JB 805 includes the set of the MWID L28 and its proximate JB 806.An FNS 820 including a group of one or more WIDs and either or both ofone or more MWIDs or MWID-JBs is provided with one direct connection tothe CCR via the master WGD 810, rather than multiple connections or theuse a secondary WGD (e.g., WGD L35 shown in FIGS. 2 and 3. For instance,the FNS 820 with WID L293, MWID L29 and MWID-JBs L292 and L291 coupledto their proximate JBs 806 effectively communicates with the CCR 801using a single connection rather than four separate connections. Theconnection between each FNS 820 and the CCR 801 can be redundant, andcan include wired, wireless or both wired and wireless connections.

Likewise, FNS 820 e at the gateway tier (tier 3) includes a modifiedwireless gateway device 813 (MWGDs), and a set 821 of a MWGD 813 devicecoupled with a JB 806 (MWGD-JB).

Network 800 includes certain FNSs 820 having MWIDs and/or MWID-JBs, andcertain FNSs having MWGDs and/or MWGD-JBs. In contrast, in networks 600of the prior art and network 700 of the present invention, the WIDs areindividual, and several nodes communicate with WGDs in tier 3. Within anFNS having MWID-JB 805, the MWID-JB 805 can be connected via a wiredinterface to one or more MWID(s) 815 and connected by wireless interfaceto traditional WIDs 814. Each set can be connected to the CCR directly(through existing wiring available via the JB), or connected wirelesslyto intermediate MWGD-JBs, or connected wirelessly to the master MWGD.Accordingly, each set can have a MWID-JB, MWGD-JB, MWID or MWGD taskedwith routing traffic to the destination.

FIG. 4 shows the detailed connectivity of the MWID-JBs to the CCR andmaster MWGD. The master MWGD will maintain the configuration of the setsincluding which MWID-JBs belong to which set, which of the MWID-JBsis/are the interface to the CCR and which one is the backup. The masterMWGD maintains the configuration of the sets including which MWIDsbelong to which FNS, and which MWID is the primary/backup within an FNSfor packet selecting functionality for each source-destination pair inthe wireless network. While the selected path for a particular sourceand destination pair may vary from one transmission to another, theanchor packet selection function within an FNS for that particularsource and destination pair generally remains constant until changed bythe master MWGD or an operator.

In general, possible sequences of packet transmission between the CCR801 and a WED 816 include, but are not limited to:

CCR 801

master WGD 810

MWGD-JB 821

MWGD 813

MWID-JB 805

MWID 815

WED 816;

CCR 801

master WGD 810

MWGD 813

MWID-JB 805

MWID 815

WED 816;

CCR 801

master WGD 810

MWGD-JB 821

MWGD 813

MWID-JB 805

MWID 815

WID 814

WED 816; or

CCR 801

master WGD 810

MWID-JB 805

MWID 815

WED 816.

The embodiment shown in FIG. 4A includes field network sets 820 (FNSs)that span two tiers. FNS 820 g spans the intermediate tier (tier 2) andthe gateway tier (tier 3), including two modified wireless intermediatedevices 815 (MWIDs) in tier 2 and one modified wireless gateway device813 (MWGD) in tier 3. FNS 820 f also spans tiers 2 and 3, with fourmodified wireless intermediate devices 815 (MWIDs) in tier 2 and onemodified wireless gateway device 813 (MWGD) with associated JB 806 intier 3.

FIG. 5 is a diagram of a network 900 according to the present inventionincluding a CCR 901 having a DCS 902 in communication with an interface908, e.g., to facilitate communication with the master WGD 910, and alsoin communication with a plurality of marshalling cabinets 904. Themaster WGD 910 can communicate with the CCR 901 (and the DCS 902 in theCCR 901) via various connections, including through interface 908 (whichcan be separate from or integrated with the DCS 902), throughmarshalling cabinets 904, through other I/O interfaces, or anycombination of these interfaces.

The network 900 includes a tier of WEDs 916 generally in communicationwith WIDs 914 and/or MWIDs 915. Furthermore, network 900 can include anexisting wired sub-network 924, e.g., having wired components connectedto a marshalling cabinet 904 in the CCR 901 through JB 906.

Further, similar to network 800 shown in FIG. 4, network 900 includes anintermediate tier having FNSs 920, and also can include one or moreindependent (i.e., not within an FNS 920) WIDs 914, MWIDs 915 andMWID-JBs 905 (having a MWID 915 and a JB 906). The FNSs 920 each includea MWID-JB 905 (although as discussed above it is possible to have an FNSwithout a MWID-JB). Further, as shown in FIG. 5, one of the FNSs 920includes a WID 914 and plural MWIDs 915. The MWID-JB sets 905 areconnected via wire to a junction box router 922 (JBR). Further, theanchor MWID/MWGD in an FNS, or an independent MWID/MWGD, can be in wiredcommunication with a JBR 922.

A third tier includes an FNS 920 having at least a MWGD-JB set 921(including a MWGD 913 and a JB 906). Note that other wireless gatewaydevices can also be included in the FNS 920 having the MWGD-JB set 921,or the MWGD-JB set 921 can be a standalone set, i.e., without theassociated FNS 920. The MWGD-JB set 921 is connected directly to themaster WGD 910 and to the MC 904. The MC 904 is connected directly tothe DCS 902.

As discussed above, the MWIDs and the MWGDs include one or more routingtables for path optimization and a packet selection module to determine,among other things, which packet of multiple packets of the same dataare to be propagated to the next tier or to the master WGD 910.

Certain MCs 904 are in communication with one or more JBRs 922 (JBR) tofacilitate integration between the plant wireless network and the plantwired network and provide suitable routing functionality andinstructions to the MWID-JBs 905. The JBRs 922 can also be wired to eachother and can be connected to the master WGD 910.

Hardwired connectivity between the master WGD 910 and a MWGD 913 or theset 921 of the MWGD-JB 921 can be via direct connection, and/or througha JBR 922 (e.g., master WGD 922 in connection with the JBR 922, which isconnected to the MWGD-JB set 921 including connection to the MWGD 913.As depicted in network 900, the set 921 of the MWGD-JB is directlyconnected to the master WGD 910.

In accordance with the present invention, a computing device 80 isprovided that executes the route optimization module 110′, theend-to-end delay minimization module 210′, the tier delay minimizationmodule 310′, the delay minimization module 410′, other modules thatapply constraints including one or more of throughput and number ofhops, or a combination including at least one of the foregoing modules,to create the routing table 190′, and downloads the resulting routingtable 190′ to the routing WIDs and WGDs (which can include MWIDs andMWGDs). In addition, the computing device 80 can execute the modules fordetermining the number and size of the FNS(s), and the anchor packetselection device for each FNS. Instructions generated by the computingdevice 80 that is a part of the DCS 902 or a separate computing devicewithin the central control room 901 are transmitted to the master WGD910, which in turn transmit the instructions to certain nodes(identified herein as the “anchor packet selection device” or “anchorpoint” within a particular FNS) in the FNSs 920. Likewise, data relatedto the delays (end-to-end and link), reliability, number of hops,throughput, field network set data, and other network statistics iscommunicated to the computing device 80, and is used to, inter alia,create or modify the routing tables and create or modify the members ofeach FNS.

As shown in FIG. 5, the JBRs 922 route wireless traffic to and from theMWID-JBs 905 to the master WGD 910 and to the DCS 902. Furthermore, theJBRs 922 route wireless traffic between an MWID-JB 905 in one FNS 920 toanother MWID-JB 905 in a different FNS 920, and between an MWID 915 inone FNS 920 to another MWID 915 in a different FNS 920.

Interconnecting JBs 906 with each other and with the wirelessinfrastructure within a commercial and industrial processing facility isa unique aspect of the present invention, for which there are noestablished standards. The network 900 of the present invention showsthe interconnectivity of JBs and the wireless plant network devices toyield improved performance and reliability. An existing wiredinfrastructure illustrated in FIG. 5 as subsystem 924 that operates in aconventional facility can continue to pass directly through one or moreMCs 904 without going to or through a JBR 922. Selected wireless andwired traffic passes through the JBRs 922. Accordingly, the presentinvention can be practiced as a stand alone system and method, e.g.,used to design and build a new or replacement process automation and/orcontrol network, or the present invention can be practiced as acomplementary network that is added onto, or modifies a portion of anexisting wired or wireless network, without changing certain existingand operational JBs or MCs (e.g., within existing subsystem 924).

FIG. 6 shows an exemplary architecture 10 of a wireless process controland/or automation system. The architecture generally follows the OpenSystems Interconnection Reference Model (OSI model), and includes: anapplication layer 12, a transport layer 14, a network layer 16, datalink layer 18 including a logical link control sublayer 20 and a mediaaccess control sublayer 22, and a physical layer 24. The applicationlayer 12 includes the functionality of presentation and session layersaccording to a wireless process control and/or automation protocol suchas the ISA-SP100 protocol, and generally provides the interface to userapplication processes. The application layer 12 further includes anapplication sublayer 26 that provides a wireless process control and/orautomation protocol interface. The transport layer 14 provides for theaddressing of user application processes via selection of a specificapplication layer entity. The network layer 16 provides network-wideaddressing of devices and relays messages between network layers ofdifferent devices. Furthermore, in accordance with embodiments of thepresent invention, the network layer supports frame routing betweensource-destination pairs based upon the route optimization modules 110and/or 110′, the end-to-end delay minimization module 210 and/or 210′,the tier delay minimization module 310 and/or 310′, the delayminimization module 410 and/or 410′, or other modules that applyconstraints including one or more of throughput and number of hops ofthe present invention. The data link layer 18 generally manages use ofthe physical layer, and includes the logical link control (LLC) sublayer20 and the medium access control (MAC) sublayer 22, and can also carryout certain optimization functionalities in the adaptive methods andsystems of the present invention, such as collecting frame error ratedata, throughput data and/or delay statistics, and passing that data tothe route optimization module 110 and/or 110′, the end-to-end delayminimization module 210 and/or 210′, the tier delay minimization module310 and/or 310′, the delay minimization module 410 and/or 410′, or othermodules that apply constraints including one or more of throughput andnumber of hops. The LLC sublayer 20 provides multiplexing and flowcontrol mechanisms, and generally acts as an interface between the MACsublayer 22 and the network layer 16. The MAC sublayer provides multipleaccess methods including the carrier sense multiple access withcollision avoidance (CSMA-CA) protocol 28 commonly used in wirelessnetworks, which is also carried out in the physical layer 24. Finally,the physical layer 24 provides bit-by-bit delivery of data, astandardized interface transmission media including radio interfacing,modulation, and physical network topology such as mesh or star networks.In addition, channel assignments and/or changes are carried out in thenetwork layer 24 and the data link layer 18.

FIG. 7 is a block diagram of a WED 30 for receiving data from, andtransmitting data to, one or more networked WIDs and/or WGDs. WED 30generally includes a processor 32, such as a central processing unit, awireless transceiver 34 and associated antenna 36, an input/outputinterface 40, a clock 45 and support circuitry 42. The processor 32,wireless transceiver 34, input/output interface 40, clock 45 and supportcircuitry 42 are commonly connected via a bus 44, which also connects toa memory 38. Memory 38 can include both volatile (RAM) and non-volatile(ROM) memory units, and stores software or firmware programs in aprogram storage portion and stores data in a data storage portion. Theinput/output interface 40 sends and receives information via acommunication link to and from the associated end devices 46, e.g.,process equipment such as meters, remote terminal units, valves,sensors, tank level measuring devices, and the like. The WED 30 cantransmit to and receive from all other devices. In a receiving mode, theWED 30 receives instructions via the antenna 32 and transceiver 34.These instructions are processed by the processor 32 and can be storedin memory 38 for later use or cached. A timestamp is preferably added tothe data using the clock 45, or alternatively, with a global positioningsystem. All devices in the network are synchronized to allow foraccurate delay calculations as described below. The instructions areconveyed to the end device via the port 40. In a transmission mode, datais conveyed from the end device to the port 40, and passed to memory 38.The data can be processed by the processor 36 including a timestampgenerated by clock 45 or other means, and sent across the networkthrough the transceiver 34 and antenna 32. The processor 32 generallyoperates using the OSI model described above for end devices, andcarries out instructions for transmission and receipt of data.

FIG. 8A is a block diagram of a WID 50 for transmitting to and receivingfrom all other devices, and for routing to other devices. WID 50generally includes a processor 52, such as a central processing unit, awireless transceiver 54 and associated antenna 56, a clock 65 andsupport circuitry 62. The processor 52, wireless transceiver 54, clock65 and support circuitry 62 are commonly connected via a bus 64, whichalso connects to a memory 58. Memory 58 commonly can include bothvolatile (RAM) and non-volatile (ROM) memory units, and stores softwareor firmware programs in a program storage portion and stores data in adata storage portion. A routing table 190 specified in accordance withthe present invention resides in memory 58, i.e., in the data storageportion. In a receiving mode, the WID 50 receives data frames via theantenna 56 and transceiver 54. The data is generally cached in memory58, for instance, for transmission when specified by the CSMA-CAprotocol, or for retransmission in the event of a failed frametransmission. In a transmission mode, data is conveyed from the memoryto the transceiver 54 under control of the processor 52. In a receivingmode, the WID 50 receives data frames via the antenna 56 and transceiver54. In a routing mode, data frames are received and transmitted. Theclock 65 or other means such as a global positioning system can addtimestamps to received, transmitted and/or routed data. The WID 50 hassufficient intelligence to be able to address and route to specificcommunication devices. The processor 52 generally operates using the OSImodel described above for intermediate devices, and carries outinstructions for transmission, receipt and routing of data.

FIG. 8B is a block diagram of an MWID 50′ for transmitting to andreceiving from all other devices, and for routing to other devices. MWID50′ is similar in function and architecture as WID 50, with the additionof a wired interface 53. As shown in FIGS. 4 and 5, the MWIDs (MWIDs 815in FIG. 4 and MWIDs 915 in FIG. 5) in the system and method of thepresent invention are in hardwired communication with other MWIDs (e.g.,within the same FNS) and with JBs. In addition, MWIDs can be provided inhardwired connection directly with the DCS in the CCR (e.g., via aninterface at the CCR) or with MWGDs. Furthermore, MWIDs 50′ can formpart of a MWID-JB set, wherein the JB is wired to the MWID via the wiredinterface 53. The routing table 190′ stored in the memory 58 of the MWID50′ includes the requisite FNSs through which assigned paths pass.Further, data 192 is also provided which includes information aboutother MWIDs, WIDs, WGDs, MWGDs, MWID-JB sets, MWGD-JB sets, and/or themaster MWGD. Data 192 is used to dynamically route data transmissions,on a packet-by-packet basis, as required.

At least certain MWIDs 50′, and in particular any MWIDs 50′ that serveas anchor packet selection devices within an FNS, also includes a packetselection module 193 and a routing module 194. Since multiple copies ofthe same transmitted packet originates from a particular source toward aparticular destination reach an anchor MWID within tier 2, the packetselection module 193 (1) selects the best packet among the variouscopies of received packets from different paths, and (2) forwards theselected packet to the next tier, either through wired or wirelesspaths, or both, depending on the reliability requirements. Further, therouting module 194 supports the architecture of the FNSs and support thepacket selection module, including modified/expanded routing tables(routing tables 190′ described herein) to support the following routingscenarios: (1) routing wireless packets to the correct JBs; (2) routingpackets to the correct anchor packet selection device for particularsource-destination pair; (3) routing packet from one FNS to another FNS,and (4) routing tables to assist in the wireless-wired networksintegration. Note that the functionalities of the packet selectionmodule 193 and a routing module 194 can be combined in a single module.

FIG. 9A is a block diagram of a WGD 70 for transmitting to and receivingfrom all other devices, for routing to other devices, and in certainembodiments of the present invention for practicing high levelapplications including protocol translation and assignment of paths forsource-destination pairs. WID 70 generally includes a processor 72, suchas a central processing unit, a wireless transceiver 74 and associatedantenna 76, a clock 85 and support circuitry 82. The processor 72,wireless transceiver 74, clock 85 and support circuitry 82 are commonlyconnected via a bus 84, which also connects to a memory 78. Memory 78commonly can include both volatile (RAM) and non-volatile (ROM) memoryunits, and stores software or firmware programs in a program storageportion and stores data in a data storage portion. A routing table 190specified in accordance with the present invention resides in memory 78,i.e., in the data storage portion. Furthermore, in certain embodimentsof the present invention, the program storage portion of the memory 78can include a routing optimization module 110 and a set of routing rules120. In receiving, transmission and routing modes, the WGD 70 operatesin a manner similar to the operation of the WID 50. The processor 72generally operates using the OSI model described above for gatewaydevices, and carries out instructions for transmission, receipt androuting of data. The WGD 70 has sufficient intelligence to be able toaddress and route to specific communication devices. In addition, incertain embodiments of the present invention, the processor 72 of theWGD 70, in particular a master WGD 70 executes the logic for the routeoptimization module 110, the end-to-end delay minimization module 210,the tier delay minimization module 310, the delay minimization module410, other modules that apply constraints including one or more ofthroughput and number of hops, or a combination including at least oneof the foregoing modules, and the path assignments are stored in therouting table 190. In embodiments where the route optimization moduleand associated logic is carried out in other computing devices, therouting table 190 can be downloaded directly to the WIDs and WGDs foruse during data routing operations, or transmitted through the wirelessnetwork in data frames and stored where required, i.e., in the routingWIDs and WGDs.

In certain embodiments of the present invention, the tier containing theWIDs can be bypassed, such that the WEDs transmit to, and receive from,WGDs. For instance, such a configuration is common in a wireless HART®protocol. In additional embodiments, WIDs can transmit frames to, andreceive frames from, other WIDs, for instance, whereby WGDs arebypassed.

FIG. 9B is a block diagram of an MWGD 70′ for transmitting to andreceiving from all other devices, for routing to other devices, and incertain embodiments of the present invention for conducting high levelapplications including protocol translation and assignment of paths forsource-destination pairs. MWGD 70′ is similar in function andarchitecture as WGD 70, with the addition of a wired interface 73. TheMWGDs in the system and method of the present invention are in hardwiredcommunication with other MWGDs, including the master WGD or master MWGD.In addition, MWGDs can be provided in hardwired connection directly withthe MWIDs, JBs or MWID-JB sets. Furthermore, MWGDs 70′ can form part ofa MWGD-JB set, wherein the JB is wired to the MWGD via the interface 73.The routing table 190′ stored in the memory 58 of the MWGD 50′ includesthe requisite FNSs through assigned paths pass. Further, data 192 isalso provided which includes information about other MWGDs, WIDs, WGDs,MWIDs, MWID-JB sets, MWGD-JB sets, and/or the master MWGD. Thisinformation is used to dynamically route data transmissions, on apacket-by-packet basis, as required.

In addition, in certain embodiments of the present invention, theprocessor 72 of the MWGD 70′, in particular a master MWGD 70′ executesthe logic for the route optimization module 110′, the end-to-end delayminimization module 210′, the tier delay minimization module 310′, thedelay minimization module 410′, other modules that apply constraintsincluding one or more of throughput and number of hops, or a combinationincluding at least one of the foregoing modules, and the pathassignments are stored in the routing table 190′. Note that modules110′, 210′, 310′ and 410′ are similar to modules 110, 210, 310 and 410,respectively, with the additional information related to the hardwiredconnections and the field network sets used to determine the routeoptimization module and associated logic. Furthermore, data 192 is alsoprovided which includes information about other MWGDs, WIDs, WGDs,MWGDs, MWID-JB sets, MWGD-JB sets, and/or the master MWGD. Data 192 isused to dynamically route data transmissions, on a packet-by-packetbasis, as required.

At least certain MWGDs 70′, and in particular any MWGDs 50′ that serveas anchor packet selection devices within an FNS, also includes a packetselection module 193 and a routing module 194. Since multiple copies ofthe same transmitted packet originates from a particular source toward aparticular destination can reach an anchor MWGD within tier 3, thepacket selection module 193 (1) selects the best packet among thevarious copies of received packets from different paths, and (2)forwards the selected packet to the master WGD or to an MC, eitherthrough wired or wireless paths, or both, depending on the reliabilityrequirements. Further, the routing module 194 supports the architectureof the FNSs and support the packet selection module, includingmodified/expanded routing tables (routing tables 190′ described herein)to support the following routing scenarios: (1) routing wireless packetsto the correct JBs; (2) routing packets to the correct anchor packetselection device for particular source-destination pair; (3) routingpacket from one FNS to another FNS, and (4) routing tables to assist inthe wireless-wired networks integration. Note that the functionalitiesof the packet selection module 193 and a routing module 194 can becombined in a single module.

FIG. 10 is a block diagram of the junction box router (JBR) 922. JBR 922generally includes a processor 972, such as a central processing unit, aclock 985, an interface 973 and support circuitry 982. The processor972, interface 973, clock 985 and support circuitry 982 are commonlyconnected via a bus 984, which also connects to a memory 978. Memory 978commonly can include both volatile (RAM) and non-volatile (ROM) memoryunits, and stores software or firmware programs in a program storageportion and stores data in a data storage portion. The data storageportion of memory 978 includes an address table 986, and the programstorage portion of the memory 978 includes a routing logic module 987and a router management diagnosis module 988.

The interface 973 serves as a routing engine that provides functionalityof a router switch, includes an interface 926 for wired connectivity toone or more MWID-JBs or MWGD-JBs, an interface 928 for wiredconnectivity to a marshalling cabinet, an interface 930 for wiredconnectivity to other JBRs or JBs (within the same FNS or differentFNS), and an interface 932 for wired connectivity to the master WGD ofthe network.

For wireless traffic routing, the MWIDs within an FNS can beinterconnected directly to other MWIDs. In certain preferredembodiments, MWIDs are interconnected through the nearest JBs and/or JBRin the CCR (e.g., MWID #1 to JB #1 to JBR to JB #2 to MWID #2), therebypermitting the various MWID-JBs and MWIDs within an FNS to operate as asingle wireless routing device covering a larger physical area in thefacility.

In addition, in accordance with the present invention, the wirelessplant network is interfaced with the wired network, advantageouslyallowing existing JBs installed in a facility, typically havingsufficient spare fiber optic/wire connectivity, to ensure that a largeportion of the wireless paths and/or links use wired connectivity. Thisreduces the wireless congestion, and improves the overall efficiency ofthe wireless network.

The following definitions and symbols are used herein in the descriptionof the route optimization module and associated system and method of thepresent invention:

i denotes usage class as described above, and can be 0, 1, 2, 3, 4 or 5;

j denotes the tier of the wireless device and can be 1, 2 or 3;

D_(i) denotes the traffic distribution, i.e., percentage of the totaltraffic, for class i;

N_(P) denotes the number of possible paths between a source and adestination;

N_(i) ^(opt) denotes the minimum or optimum number of paths for asource-destination pair in usage class i;

x denotes the path number, i.e. x=1, 2, 3, . . . , N_(P); e.g., x=5 meanthe 5^(th) path out of N_(P) paths;

|L(x)| denotes the number of intermediate links for the x-th path;

|L_(i) ^(opt)| denotes the maximum number of intermediate links for apath for a source-destination pair in usage class i;

L(x,y) denotes the y-th link of the x-th path, for y=1, 2, 3, . . . ,|L(x)|;

Φ(L(x,y)) denotes the frame error probability for the y-th link of thex-th path, and the link reliably profile is a matrix consisting of all[1−Φ(L(x,y))];

Φ(x) denotes the frame error probability for the x-th path, e.g., Φ(2)is the frame error probability of path 2, Φ(2,5) is the effective frameerror probability for the combined path 2 and 5;

1−Φ_(c)(i) denotes the end-to-end reliability requirements for class i;

Φ_(c)(i) denotes the end-to-end frame error probability requirements forclass i;

α denotes the maximum allowable frame error probability for a singlelink;

η(L(x,y)) is the existing throughput for the y-th link of the x-th path;

η(L(x,y),max) is the maximum throughput for the y-th link of the x-thpath;

ψ(j,i,x) denotes the calculated delay in tier j for class i goingthrough path x, and the tier delay profile is a matrix for all ψ(j,i,x);

ψ(i,j,max) denotes the maximum allowable delay in tier j for class i;

ψ(i,x) denotes the calculated delay for a particular path x for class i;and

ψ(i,max) denotes the maximum allowable end-to-end delay for class i.

Table 1 represents process control system requirements based upon eachusage class:

TABLE 1 Traffic Reliability Class Distribution Requirements DelayRequirements (i) Class Description D_(i) 1-Φ_(c)(i) ψ(i, j, max), ψ(i,max) 0 Safety & Emergency Actions D₀ 1-Φ_(c)(0) ψ(0, j, max), ψ(0, max)1 Closed-Loop Regulatory Control D₁ 1-Φ_(c)(1) ψ(1, j, max), ψ(1, max) 2Closed-Loop Supervisory Control D₂ 1-Φ_(c)(2) ψ(2, j, max), ψ(2, max) 3Open-Loop Control D₃ 1-Φ_(c)(3) ψ(3, j, max), ψ(3, max) 4 Alerting D₄1-Φ_(c)(4) ψ(4, j, max), ψ(4, max) 5 Logging D₅ 1-Φ_(c)(5) ψ(5, j, max),ψ(5, max)

The following description and related equations set forth an exemplaryprocess and route optimization module for determining and assigning oneor more reliable paths for a source-destination pair. However, one ofordinary skill in the art will appreciate that deviations from the setof equations that follow, including variations in sequence and precisedefinition of terms, can result in the same or an equivalentdetermination and assignment. Accordingly, in accordance with anembodiment of the present invention, the method steps described withrespect to FIGS. 14A and 14B, FIGS. 15A and 15B, FIGS. 16A and 16B,FIGS. 17A and 17B, and variations thereof, are implemented as a module,or set of instructions, in a computing device, which can include a WGDor a separate computing device. In the case of the module being executedby a WGD, the module can be executed in a master wireless gatewaydevice, for instance, located in the CCR, or alternatively by one ormore of the additional wireless gateway devices within tier 3.

In embodiments in which the one or more modules 110, 210, 310, 410 areexecuted by a separate computing device, the end results, i.e., theassignment and determination of one or more reliable paths between aselected source-destination pair, can be ascertained and uploaded to oneor more of the wireless gateway devices. In certain embodimentsemploying a separate computing device, an adaptive system is providedwhereby communication between the separate computing device and one ormore WGDs is maintained continuously (wired or wireless). In an adaptivesystem, one or more WGDs can be programmed to look to the separatecomputing device to determine and assign new paths between one or moreselected source-destination pairs. In alternative embodiments, the WGDsand WIDs can communicate with the separate computing device periodicallyto receive updates. In further alternative embodiments, one or more WGDsand/or WIDs can instruct the separate computing device to execute theroute optimization module of the present invention to alter assignmentswhen performance degradation is detected, for example, in the case ofone or more bad links or nodes within the wireless process controland/or automation network.

An exemplary block diagram of a computer system 80 by which the routeoptimization module of the present invention can be implemented is shownin FIG. 11. Computer system 80 includes a processor 82, such as acentral processing unit, an input/output interface 90 and supportcircuitry 92. In certain embodiments, where the computer 80 requires adirect human interface, a display 96 and an input device 98 such as akeyboard, mouse or pointer are also provided. The display 96, inputdevice 98, processor 82, and support circuitry 92 are shown connected toa bus 94 which also connects to a memory 88. Memory 88 includes programstorage memory 111 and data storage memory 191. Note that while computer80 is depicted with direct human interface components display 96 andinput device 98, programming of modules and exportation of data canalternatively be accomplished over the interface 90, for instance, wherethe computer 80 is connected to a network and the programming anddisplay operations occur on another associated computer, or via adetachable input device as is known with respect to interfacingprogrammable logic controllers.

Program storage memory 111 and data storage memory 191 can each comprisevolatile (RAM) and non-volatile (ROM) memory units and can also comprisehard disk and backup storage capacity, and both program storage memory111 and data storage memory 191 can be embodied in a single memorydevice or separated in plural memory devices. Program storage memory 111stores software program modules and associated data, and in particularstores a route optimization module 110, the end-to-end delayminimization module 210, the tier delay minimization module 310, thedelay minimization module 410, other modules that apply constraintsincluding one or more of throughput and number of hops, or a combinationincluding at least one of the foregoing modules. Data storage memory 191stores a set of routing rules 120 and a routing table 190 generated bythe one or more modules of the present invention.

It is to be appreciated that the computer system 80 can be any computersuch as a personal computer, minicomputer, workstation, mainframe, adedicated controller such as a programmable logic controller, or acombination thereof. While the computer system 80 is shown, forillustration purposes, as a single computer unit, the system cancomprise a group/farm of computers which can be scaled depending on theprocessing load and database size. In addition, as described above, thefunctionality of the computer system 80 can be executed by one or moreof the WGDs, MWGDs, and/or within the DCS.

The computing device 80 preferably supports an operating system, forexample stored in program storage memory 111 and executed by theprocessor 82 from volatile memory. According to an embodiment of theinvention, the operating system contains instructions for interfacingthe device 80 to the wireless process control and/or automation network,including the route optimization module of the present invention as morefully discussed herein.

FIG. 12 shows six (6) types of traffic transmitted between the sourceand the destination. Assignment of paths is determined in a manner tomeet the usage class performance requirement. For instance, instead ofhaving 4 paths to cover all traffic between a source and a destination,paths are assigned per usage class performance requirement.

FIG. 13 is a block diagram representing the optimization framework inaccordance with the present invention. A suitable computer (e.g.,computer 80 provided in the CCR and/or at the master WGD) executes a setof modules 1010, 1020, 1030 and 1040. Module 1010 determines thearchitecture configuration of JBs, MWIDs and MWGDs. Module 1020determines the configuration of the FNSs, including the number of FNSs,the size of each FNS (i.e., number of components), and the area of theplant that each FNS shall encompass. Module 1030 is a path optimizationmodule. Module 1040 is a packet selection module. The modules 1010,1020, 1030 and 1040 are executed based on objectives 1050, inputs 1060,and constraints 1070, and generate outputs 1080.

Objectives 1050 include minimization of the number of paths andtransmitted packets for each source-destination pair per usage class.Inputs 1060 include the plant layout (e.g., the physical location of theend devices and existing control/automation intermediate and gatewaydevices), traffic distribution, location of junction boxes, networkstatistics, the number of WIDs and MWIDs, the number of WGDs and MWGDs,and the usage classes. Constraints 1070 include the throughput per link,the reliability per link, the end-to-end reliability, the number ofneighboring FNSs, maximum allowable tier delay and end-to-end delay, andallowable processor loading of an MWID (e.g., the anchor MWID) forpacket selection in FNSs. The outputs 1080 include the assigned andalternate paths for each source-destination pair per usage class, forinstance, in the form of a routing table.

FIG. 14A is a schematic block diagram of a wireless process controland/or automation network routing system 100 according to an embodimentof the present invention. In general, the wireless process controland/or automation network routing system 100 includes a routeoptimization module 110, a set of routing rules 120, e.g., in the formof a routing table, and hardware 80 for executing the route optimizationmodule 110 based on the set of routing rules 120. In general, the routeoptimization module 110 is executable by suitably interconnectedhardware 80, such as one or more wireless gateway devices 80 a, aseparate computing device 80 b, a combination of one or more wirelessgateway devices 80 a and a separate computing device 80 b, or otherknown processing device.

The set of routing rules 120 is commonly in the form of a rule table,although one of ordinary skill in the art of computer science willappreciate that the set of rules can be in a format other than a table,e.g., a database, a directory, or other type of file structure. The setof routing rules 120 in the form of a rule table includes a sourcecolumn 122, a destination column 124, a usage class column 126, aminimum reliability requirement 1−Φ_(c)(i) column 128 and a column 130specifying the minimum number of paths N_(i) ^(opt) in asource-destination pair per usage class. In general, the rules arespecified for end-to-end source-destination pairs, although in certainembodiments it can be desirable to specify rules for othersource-destination pairs. For example, a destination WGD can be providedwith communication to the CCR outside of the route optimization module110 of the present invention. The route optimization module 110 usesthis set of routing rules 120 in certain steps or sub-modules asdescribed further herein. The set of routing rules 120 can be stored inthe hardware 80, or in a separate and accessible computer memory device,depending, for instance, upon the desired system configuration.

Still referring to FIG. 14A, and also referring to FIG. 14B, theoperation of an embodiment of the route optimization module 110 is shownin more detail. A path determination sub-module 150 determines at step152 possible paths between a selected source-destination pair. Forexample, referring to FIG. 3, for the source-destination pair of thewireless end device L17 and the wireless gateway device L35, thewireless paths shown by dashed lines include:

(i) L17-L293-L292-L36-L35;

(ii) L17-L293-L29-L36-L35;

(iii) L 17-L293-L29-L34-L35;

(iv) L17-L291-L292-L36-L35;

(v) L17-L291-L292-L34-L35;

(vi) L17-L291-L28-L34-L35;

(vii) L17-L293-L292-L291-L28-L34-L35;

(viii) L 17-L291-L292-L293-L29-L36-L35; and

(ix) L17-L291-L292-L293-L29-L34-L35.

For the source-destination pair of the wireless end device L13 and thewireless gateway device L31 at the central control room, the paths shownby dashed lines include:

(i) L13-L23-L24-L32-L31;

(ii) L13-L23-L32-L31;

(iii) L13-L24-L23-L32-L31;

(iv) L13-L24-L32-L31;

(v) L13-L24-L25-L32-L31;

(vi) L13-L24-L25-L26-L32-L31;

(vii) L13-L25-L32-L31;

(viii) L13-L26-L32-L31

(ix) L13-L25-L24-L32-L31;

(x) L13-L26-L25-L32-L31; and

(xi) L13-L26-L25-L24-L32-L31.

Note that while paths show that data frames generally hop from a tier 1node to one or more tier 2 nodes, and then to one or more tier 3 nodes,in certain embodiments a path can include data frames that hop from atier 2 node to a tier 3 node, back to a tier 2 node and back to a tier 3node, whereby duplication of nodes within a path is generally avoided.However, as described further herein, such paths having a larger numberof hops will likely be eliminated from consideration in preferredembodiments of the present invention. Of course, one of ordinary skillin the art will recognize that other paths not specifically marked inFIG. 3 are possible.

Next, a reliability calculation sub-module 160 calculates at step 162the reliability of each of the possible paths, calculated from a linkreliability profile. In certain alternative embodiments, the listing ofall of the paths can be preliminarily filtered to eliminate those thatare greater than a maximum number of links for a given usage class i,|L_(i) ^(opt)|. For example, if |L_(i) ^(opt)| is specified as five forall usage classes, an excessive path link filter sub-module can beapplied to discard from the routing table 190 paths with more than fivelinks, i.e., |L(x)|>|L_(i) ^(opt)|, such as paths (vii), (viii) and (ix)of the source-destination pair of the wireless end device L17 and thewireless gateway device L35. Likewise, an excessive path link filtersub-module can be applied to discard from the routing table 190 paths(vi) and (xi) related to the source-destination pair of the wireless enddevice L13 and the wireless gateway device L31.

In additional and/or alternative embodiments, as described furtherherein, the link reliability profile data can be obtained from empiricaldata of frame error rates of each link, or derived from estimatescalculated based upon the type of hardware and network loading. Forinstance, an exemplary profile of link FER values is given in Table 2below:

TABLE 2 Link FER Source Destination Φ(L(x, y)) L13 L23 1.00E−05 L13 L241.00E−06 L13 L25 5.00E−07 L13 L26 1.00E−07 L23 L32 5.00E−04 L24 L325.00E−06 L25 L32 5.00E−04 L26 L32 5.00E−03

The reliability 1−Φ(x) for a path x is calculated from the linkreliability profile data in Table 2 as follows:

$\begin{matrix}{{1 - {\Phi (x)}} = {\prod\limits_{y = 1}^{{L{(x)}}}\; \left( {1 - {{\Phi \left( {L\left( {x,y} \right)} \right)}.}} \right.}} & (1)\end{matrix}$

Calculations in accordance with Equation (1) are repeated for each pathx for each source-destination pair.

It is noted that a link in a path having a relatively low reliabilitywill adversely affect the entire path performance, even if the remaininglinks have relatively high reliabilities. Therefore, it is advantageousto provide links with a small variance in reliability within a path. Incertain preferred embodiments, this is accomplished by ensuring that:

Φ(L(x,y))≦α for all y  (2).

Paths x that include links y that do not meet Equation (2) areeliminated from consideration.

It is well known that the simultaneous transmission of a frame over twoindependent paths connecting a source and destination creates a higherreliability than if the frame were only transmitted via a single path.Applied to the present invention, when combining two independent paths,namely x₁ and x₂, the effective reliability is expressed as:

1−Φ(x ₁ ,x ₂)=1−Φ(x ₁)*Φ(x ₂)  (3),

and for N_(P) independent paths, the effective reliability of thecombined N_(P) paths, denoted by 1−Φ(x₁, x₂, . . . , x_(N) _(p) ) isgiven by:

$\begin{matrix}{{1 - {\Phi \left( {x_{1},x_{2},\ldots \mspace{14mu},x_{N_{p}}} \right)}} = {1 - {\prod\limits_{w = 1}^{N_{p}}\; {\left( {\Phi \left( x_{w} \right)} \right).}}}} & (4)\end{matrix}$

In certain embodiments, in addition to calculating the reliability ofeach of the possible paths, or effective reliability of groups of paths,at step 162, sub-module 160 or another sub-module (not shown) performsan optional step 163 (shown by dashed lines) in which the throughput,number of hops, delay (tier and/or end-to-end), or a combination of oneor more of throughput, number of hops and delay, for each of thepossible paths is determined or calculated. This determination orcalculation can be used in path selection to assign one or more pathsthat meet multiple constraints.

In additional embodiments, sub-module 160, and in particular step 162and optionally step 163, considers statistics from the wireless processcontrol and/or automation network, indicated by step 164 in dashedlines. Step 162 can determine reliability of each of the possible pathsbased on frame error rate statistics determined at each link, nodeand/or path. In addition, step 163 can obtain statistics at step 164related to one or more of determined reliability, calculated throughput,calculated end-to-end delay and calculated tier delay.

A reliable path identification sub-module 170, at step 172 identifiesand selects a path, i.e., reliable paths 1−Φ(x), or set of paths, i.e.,1−Φ(x₁, x₂) or 1−Φ(x₁, x₂, . . . , x_(N) _(p) ), from the possible pathsx between a selected source-destination pair. The selected path or setof paths is identified by comparison to the minimum reliabilityrequirements 1−Φ(i) specified in the set of routing rules 120.Accordingly, paths meeting the following conditions are identified asreliable:

1−Φ(x)≧1−Φ(i) for each usage class  (5),

and

L(x) is smallest  (6).

Note that in circumstances in which combined independent paths areselected, i.e., a selected group of paths, the comparison of Equation(5) is carried out substituting 1−Φ(x₁, x₂) calculated from Equation (3)or 1−Φ(x₁, x₂, . . . , x_(N) _(p) ) calculated from Equation (4) for1−Φ(x).

In certain embodiments, the paths and/or group of paths can be selectedbased on the condition that |L(x)| satisfies the following constraint:

|L _(i) ^(opt) |≧|L(x)|  (7).

Finally, a path assignment sub-module 180 assigns at step 182 theminimum number of reliable paths for the selected source-destinationpair based on the minimum number of paths N_(i) ^(opt) for asource-destination pair specified in the set of routing rules 120. Thesepaths can be then assigned in a path routing table 190, where thenotations “A,” “B,” “C” and “D” refer to different paths that meet theconditions of Equation (5) and have the lowest |L(x)|. Where the numberof paths having the lowest |L(x)| value do not meet the minimum numberof paths N_(i) ^(opt) for a source-destination pair, the path(s) havingthe next largest |L(x)| are assigned so that the minimum number of pathsN_(i) ^(opt) for a source-destination pair is provided. In thealternative, the paths selected satisfy the conditions of Equation (7).As described further herein, in optional embodiments of the presentinvention, at step 182, the path assignment sub-module 180 alsoconsiders additional constraints in assigning paths to the path routingtable 190, including throughput, delay (end-to-end and/or tier), numberof hops, or a combination of one or more of throughput, number of hopsand delay, as indicated by step 183 in dashed lines.

Furthermore, in additional embodiments of the present invention, thepath assignment step 182 is iterative, wherein, based upon networkstatistics related to one or more of calculated reliability, number ofhops, calculated throughput, calculated end-to-end delay and calculatedtier delay, certain paths are discarded and replaced with additionalpaths to meet the minimum number of paths for a source-destination pair.This optional embodiment allows the system and method to be adaptive tocontinuously maintain optimal network traffic flow, and is comprehendedin FIG. 14B with a dashed connector between steps 162 and 182.

In certain embodiments, several combinations of paths or groups of pathswill meet the requirements of Equations (5)-(6). In these cases, theselection of the paths should seek a uniform distribution of trafficover the network. The method of the present invention therefore assignsthe minimum number of paths N_(i) ^(opt) for a source-destination pairand in certain embodiments additional alternate paths. For instance, asshown in path routing table 190, up to two alternate paths are provided.The remaining set of paths N_(p)(N_(i) ^(opt)+2) are discarded.

For a particular source-destination pair, during normal operatingconditions, data traffic is routed through the assigned paths ratherthan the alternate paths. However, if degradation in the usage classperformance is sensed at either end, or at one of the links or nodes inan assigned path, data traffic passes through both the assigned pathsand the alternate paths.

In certain alternative embodiments of the present invention, the minimumnumber of paths for a source-destination pair is dynamically adjustedbased on the usage class reliability requirements 1−Φ_(c)(i) andvariations in network and/or traffic loading. The minimum number ofpaths N_(i) ^(opt) that meet the network reliability requirements can bedetermined such that:

Φ(N _(i) ^(opt))≦Φ_(c)(i), for all i  (8).

In an additional embodiment of the present invention, consideration isgiven to a maximum allowable delay in assignment of particular paths fora source-destination pair. Accordingly, if the calculated delay exceedsthe maximum allowable delay for a given path, another path, e.g., a setof WED, WID, and/or WGD, can be added to minimize delay. Alternatively,or in conjunction, another radio frequency channel and/or hoppingpattern can be employed to minimize delay for the given path.

In certain embodiments in which the path assignment is based on usageclass, one or more paths x are assigned such that the followingconditions are satisfied:

ψ(j,i,x)≦ψ(j,i,max) for all j, i, and x  (9a),

and

ψ(i,x)≦ψ(i,max) for all i and x  (9b).

Paths x that do not meet the conditions of Equation (9a) or Equation(9b) are discarded in this embodiment.

In certain embodiments of the present invention, the maximum allowabledelay is considered in selecting the minimum number of paths N_(i)^(opt) for a source-destination pair based on satisfaction of Equations(9a) and (9b).

In further embodiments of the present invention, the method and systemof the present invention defines a maximum allowable delay for frametransmission within each tier j, ψ(i,j,max), as a function of the classi. The sum of all values ψ(i,j,max) for all j should not exceed themaximum system delay constraints. Because wireless process controland/or automation networks can be sensitive to delay, maintaining thetransport delay at each tier within the system maximum allowable delayis desirable to ensure proper operation.

FIG. 14C is a flow process diagram illustrating the operation of anembodiment of a route optimization module 110′ adapted to prepare arouting table 190′ in a system including FNSs. A path determinationsub-module 150 determines at step 152′ possible paths between a selectedsource-destination pair. Note that step 152′ is similar to step 152 ofroute optimization module 110, with the additional constraint that thepaths determination for each source-destination pair requires passagethrough the anchor packet selection device, e.g., an MWID or in certaininstances an MWGD. This is determined for N neighboring FNSs, wherein Nis a predetermined value depending on various factors. In certainembodiments, N can be selected as three (3), however this value can beincreased. Preferably it is not reduced below 3, as the lowest value forthe minimum number of paths N_(i) ^(opt) in the set of routing rules 120is generally 2, and it is desirable assign paths that pass throughdifferent FNSs.

In addition, the optional steps 163′ and 183′ are modified in module110′ as compared to steps 163 and 183 of module 110 by the inclusion ofthe number of neighboring FNSs and CPU loading of the MWID (for packetselection module).

The result of execution of the route optimization module 110′ is thecreation of the routing table 190′ as shown in FIG. 14D. Routing table190′ is similar to routing table 190, with the inclusion of columns forassigned FNSs, assigned anchor packet selection (PS) device, alternateFNSs and alternate anchor packet selection for each source-destinationpair. For instance, as shown in FIG. 14D, path “A” includes the assignedanchor path selection device “4” in FNS “I”; path “B” includes theassigned anchor path selection device “7” in FNS “III”; path “C”includes the assigned anchor path selection device “1” in FNS “V”; andpath “D” includes the assigned anchor path selection device “5” in FNS“II.”

In certain embodiments of the present invention, certain paths havingwired connectivity are selected by the route optimization module 110′ asat least one of the assigned paths for a source-destination pair for agive usage class, presuming that such paths exceed the reliability ofpaths that are entirely or substantially wireless. If more than onehardwired path is available, they will both be used as assigned pathsand/or alternative paths. In further embodiments, for eachsource-destination pair, at least one wireless path is selected as anassigned or alternate path in the event that a hardwired link to the CCRis disabled, due to an unexpected failure or an anticipateddisconnection (e.g., for service or maintenance). Furthermore, ifmultiple paths are required to meet a usage class requirement, inpreferred embodiments paths are selected for routing table 190′ thatpass through different FNSs.

FIG. 15A is a schematic block diagram of a wireless process controland/or automation network routing system 200 according to anotherembodiment of the present invention. In general, the wireless processcontrol and/or automation network routing system 200 includes anend-to-end delay minimization module 210, a set of maximum allowableend-to-end delay rules 220, e.g., in the form of a maximum allowableend-to-end delay table, and hardware 80 for executing the delayminimization module 210. In general, the delay minimization module 210is executable by suitably interconnected hardware 80, such as one ormore wireless gateway devices 80 a, a separate computing device 80 b, acombination of one or more wireless gateway devices 80 a and a separatecomputing device 80 b, or other known processing device. The end-to-enddelay minimization module 210 generally includes a path determinationsub-module 150, an end-to-end delay calculation sub-module 260, a pathidentification sub-module 270 and a path assignment sub-module 280.

Still referring to FIG. 15A, and also referring to FIG. 15B, theoperation of an embodiment of the end-to-end delay minimization module210 is shown in more detail. A path determination sub-module 150determines at step 152 possible paths between a selectedsource-destination pair. This step 152 and module 150 operate, forinstance, in the same manner as described above with respect to FIGS.14A and 14B.

Next, the end-to-end delay calculation sub-module 260 calculates at step262 the end-to-end delay for each of the possible paths determined instep 152. These calculations can be based upon network statisticsincorporated at step 264. For instance, each transmitted frame includesa timestamp with the time at which frame processing commences at thesource. When the frame is received by the destination, a receipttimestamp is incorporated, and the end-to-end delay can be calculatedbased on the difference between the receipt time of the destination andthe time that frame processing commenced at the source. This calculationaccounts for all frame or packet processing time and transmission timeat each node in the path.

In certain embodiments, in addition to calculating the end-to-end delayof each of the possible paths at step 262, sub-module 260 or anothersub-module (not shown) performs an optional step 263 (shown by dashedlines) in which the reliability, throughput, number of hops, tier delay,or a combination of one or more of reliability, throughput, number ofhops and tier delay, for each of the possible paths is determined orcalculated. This determination or calculation can be used in pathselection to assign one or more paths that meet multiple constraints.

Next, at step 272, the path identification sub-module 270 identifiesacceptable paths by comparison of the calculated end-to-end delay withthe maximum allowable end-to-end delay specified in the set of maximumallowable end-to-end delay rules 220. The set of maximum allowableend-to-end delay rules 220 includes, in certain embodiments, specifiedmaximum allowable end-to-end delay 224 per usage class 222, denoted asψ(i,max). Paths are identified as acceptable if Equation (9b) set forthabove is satisfied.

Finally, a path assignment sub-module 280 assigns at step 282 theacceptable paths, i.e., paths that satisfy Equation (9b), to the routingtable 190. In additional embodiments of the present invention, at step282, the path assignment sub-module 280 also considers additionalconstraints in assigning paths to the path routing table 190, includingminimum reliability (e.g., following the module 110 described withrespect to FIGS. 14A and 14B),maximum throughput, a maximum allowabletier delay, maximum number of hops, or a combination of one or more ofminimum reliability, maximum throughput, maximum number of hops andminimum allowable tier delay, as indicated by step 283 in dashed lines.

During network transmission incorporating the system and method of thepresent invention, if a frame is received at the destination with acalculated end-to-end delay that exceeds the maximum allowableend-to-end delay, the path through which that frame passed will beidentified in the network statistics as unacceptable for failing tosatisfy the end-to-end delay constraint. This information will be usedto dynamically discard that failed path from the routing table 190, andreplace that path with one or more additional paths, for instance, ifnecessary to meet any other specified constraints.

In addition, in still further embodiments of the present invention, thepath assignment step 282 is iterative, wherein, based upon networkstatistics related to one or more of calculated reliability, calculatedthroughput, number of hops and calculated tier delay, certain paths arediscarded and replaced with additional paths. The iterative nature ofthe end-to-end delay minimization module 210 allows the system andmethod to be adaptive to continuously maintain optimal network trafficflow, and is comprehended in FIG. 15B with a dashed connector betweensteps 262 and 282.

FIG. 15C is a flow process diagram illustrating the operation of anembodiment of an end-to-end delay minimization module 210′ adapted toprepare a routing table 190′ in a system including FNSs. A pathdetermination sub-module 150 determines at step 152′ possible pathsbetween a selected source-destination pair. Step 152′ includes theadditional constraints (as compared to step 152 of end-to-end delayminimization module 210) described with respect to the routeoptimization module 110′, i.e., that the paths determination for eachsource-destination pair requires passage through the anchor packetselection device for N neighboring FNSs

In addition, the optional steps 263′ and 283′ are modified in module210′ as compared to steps 263 and 283 of module 210 in a similar manneras described with respect to steps 163′ and 183′ in the routeoptimization module 110′, i.e., by the inclusion of the number ofneighboring FNSs and CPU loading of the MWID (for packet selectionmodule).

The result of execution of the end-to-end delay minimization module 210′is the creation of the routing table 190′ as shown in FIG. 15D. Notethat this routing table is similar to that shown with respect to FIG.14D, with the elimination of the alternate paths, but the alternatepaths can also be provided in the routing table 190′ created using theend-to-end delay minimization module 210′. Routing table 190′ as shownin FIG. 15D is similar to routing table 190 shown in FIG. 15B, with theinclusion of columns for assigned FNSs and assigned anchor packetselection (PS) devices.

In certain embodiments of the present invention, certain paths havingwired connectivity are selected by the end-to-end delay minimizationmodule 210′ as at least one of the assigned paths for asource-destination pair for a give usage class, presuming that suchpaths have an end-to-end delay that is less than that of paths that areentirely or substantially wireless. If more than one hardwired path isavailable, they will both be used as assigned paths and/or alternativepaths. In further embodiments, for each source-destination pair, atleast one wireless path is selected as an assigned or alternate path inthe event that a hardwired link to the CCR is disabled, due to anunexpected failure or an anticipated disconnection (e.g., for service ormaintenance). Furthermore, if multiple paths are required to meet ausage class requirement, in preferred embodiments paths are selected forrouting table 190′ that pass through different FNSs.

FIG. 16A is a schematic block diagram of a wireless process controland/or automation network routing system 300 according to yet anotherembodiment of the present invention. In general, the wireless processcontrol and/or automation network routing system 300 includes a tierdelay minimization module 310, a set of maximum allowable tier delayrules 320, e.g., in the form of a maximum allowable tier delay table,and hardware 80 for executing the delay minimization module 310. Ingeneral, the delay minimization module 310 is executable by suitablyinterconnected hardware 80, such as one or more wireless gateway devices80 a, a separate computing device 80 b, a combination of one or morewireless gateway devices 80 a and a separate computing device 80 b, orother known processing device. The tier delay minimization module 310generally includes a path determination sub-module 150, a tier delaycalculation sub-module 360, a link identification sub-module 370 and apath assignment sub-module 380.

Still referring to FIG. 16A, and also referring to FIG. 16B, theoperation of an embodiment of the tier delay minimization module 310 isshown in more detail. A path determination sub-module 150 determines atstep 152 possible paths between a selected source-destination pair. Thisstep 152 and module 150 operate, for instance, in the same manner asdescribed above with respect to FIGS. 14A and 14B.

Next, the tier delay calculation sub-module 360 calculates at step 362the tier delay for each of the links or set of links in tier j for thepossible paths determined in step 152. These calculations can be basedupon network statistics incorporated at step 364. For instance, eachtransmitted frame includes a timestamp with the time at which frameprocessing commences at the source. When the frame is transmitted fromthe last node in the given tier, a transmission timestamp isincorporated, and the tier delay can be calculated based on thedifference between the transmission time at the last node in the tier jand the time that frame processing commenced at the first node in thetier j. This calculation accounts for all frame or packet processingtime and transmission time at each node in the path in tier j.

In certain embodiments, in addition to calculating the tier delay ofeach of the possible paths at step 362, sub-module 360 or anothersub-module (not shown) performs an optional step 363 (shown by dashedlines) in which the reliability, throughput, number of hops, end-to-enddelay, or a combination of one or more of reliability, throughput,number of hops and end-to-end delay, for each of the possible paths isdetermined or calculated. This determination or calculation can be usedin path selection to assign one or more paths that meet multipleconstraints.

Next, at step 372, the link identification sub-module 370 identifiesacceptable links or sets of links by comparison of the calculated tierdelay with the maximum allowable tier delay specified in the set ofmaximum allowable tier delay rules 320. The set of maximum allowabletier delay rules 320 includes, in certain embodiments, specified maximumallowable tier delay 326 per usage class i 322 per tier j 328, denotedas ψ(j,i,max). A link or a set of links is identified as acceptable ifEquation (9a) set forth above is satisfied. The steps 362 and 372 arerepeated for each tier j within a path, or unless a calculated tierdelay exceeds the maximum allowable tier delay, at which point the pathis discarded.

Finally, after Equation (9a) is satisfied for all tiers within a givenpath, the path assignment sub-module 380 assigns at step 382 theacceptable paths to the routing table 190. In additional embodiments ofthe present invention, at step 382, the path assignment sub-module 380also considers additional constraints in assigning paths to the pathrouting table 190, including reliability (e.g., following the module 110described with respect to FIGS. 14A and 14B), throughput, a maximumallowable end-to-end delay, number of hops, or a combination of one ormore of throughput, number of hops and tier delay, as indicated by step383 in dashed lines.

During network transmission incorporating the system and method of thepresent invention, if a frame is received at the end of a tier with acalculated tier delay that exceeds the maximum allowable tier delay,that frame will be dropped, and the link or set of links within the tierwill be identified in the network statistics as unacceptable as failingto satisfy the end-to-end delay constraint. This information will beused to dynamically discard the one or more paths including that link orset of links from the routing table 190, and replace the one or morediscarded paths with one or more additional paths, for instance, ifnecessary to meet any other specified constraints.

In addition, in still further embodiments of the present invention, thepath assignment step 382 is iterative, wherein, based upon networkstatistics related to one or more of calculated reliability, calculatedthroughput, number of hops and calculated tier delay, certain paths arediscarded and replaced with additional paths. The iterative nature ofthe tier delay module 310 allows the system and method to be adaptive tocontinuously maintain optimal network traffic flow, and is comprehendedin FIG. 16B with a dashed connector between steps 362 and 382.

FIG. 16C is a flow process diagram illustrating the operation of anembodiment of a tier delay minimization module 310′ adapted to prepare arouting table 190′ in a system including FNSs. A path determinationsub-module 150 determines at step 152′ possible paths between a selectedsource-destination pair. Step 152′ includes the additional constraints(as compared to step 152 of tier delay minimization module 310)described with respect to the route optimization module 110′, i.e., thatthe paths determination for each source-destination pair requirespassage through the anchor packet selection device for N neighboringFNSs

In addition, the optional steps 363′ and 383′ are modified in module310′ as compared to steps 363 and 383 of module 310 in a similar manneras described with respect to steps 163′ and 183′ in the routeoptimization module 110′, i.e., by the inclusion of the number ofneighboring FNSs and CPU loading of the MWID (for packet selectionmodule).

The result of execution of the tier delay minimization module 310′ isthe creation of the routing table 190′ as shown in FIG. 14D or 15D.

In certain embodiments of the present invention, certain paths havingwired connectivity are selected by the tier delay minimization module310′ as at least one of the assigned paths for a source-destination pairfor a give usage class, presuming that such paths have a tier delay thatis less than that of paths that are entirely or substantially wireless.If more than one hardwired path is available, they will both be used asassigned paths and/or alternative paths. In further embodiments, foreach source-destination pair, at least one wireless path is selected asan assigned or alternate path in the event that a hardwired link to theCCR is disabled, due to an unexpected failure or an anticipateddisconnection (e.g., for service or maintenance). Furthermore, ifmultiple paths are required to meet a usage class requirement, inpreferred embodiments paths are selected for routing table 190′ thatpass through different FNSs.

FIG. 17A is a schematic block diagram of a wireless process controland/or automation network routing system 400 according to still anotherembodiment of the present invention. In general, the wireless processcontrol and/or automation network routing system 400 includes a delayminimization module 410, a set of maximum allowable delay rules 420,e.g., in the form of a maximum allowable delay table incorporatingmaximum allowable tier delay values 426 for tiers j 428 in a given usageclass i 422 and maximum allowable end-to-end delay values 424 for agiven usage class i 422, and hardware 80 for executing the delayminimization module 410. In general, the delay minimization module 410is executable by suitably interconnected hardware 80, such as one ormore wireless gateway devices 80 a, a separate computing device 80 b, acombination of one or more wireless gateway devices 80 a and a separatecomputing device 80 b, or other known processing device. The tier delayminimization module 410 generally includes a path determinationsub-module 150, an end-to-end delay calculation sub-module 460, apotentially acceptable path identification sub-module 465, a tier delaycalculation sub-module 470, a link identification sub-module 475 and apath assignment sub-module 480.

Still referring to FIG. 17A, and also referring to FIG. 17B, theoperation of an embodiment of the delay minimization module 410 is shownin more detail. While the steps of incorporating network statistics, anddetermining and employing the additional factors including reliability,throughput and total number of hops for the assignment of paths, are notspecifically shown with respect to FIG. 17B for sake of clarity, one ofskill in the art will appreciate based on the previous embodimentsdescribed herein that these additional steps can be incorporated in themodule 410.

As shown in FIG. 17B, a path determination sub-module 150 determines atstep 152 possible paths between a selected source-destination pair. Thisstep 152 and module 150 operate, for instance, in the same manner asdescribed above with respect to FIGS. 14A and 14B.

Next, the end-to-end delay calculation sub-module 460 calculates at step462 the end-to-end delay for each of the possible paths determined instep 152. These calculations can be based upon network statistics (notshown in FIG. 17B), for instance, as discussed with respect to FIG. 15A(reference numeral 264). For instance, each transmitted frame includes atimestamp with the time at which frame processing commences at thesource. When the frame is received by the destination, a receipttimestamp is incorporated, and the end-to-end delay can be calculated.This calculation accounts for all frame or packet processing time andtransmission time at each node in the path.

In certain embodiments, for instance, as depicted in FIG. 15A (referencenumeral 263), in addition to calculating the end-to-end delay of each ofthe possible paths at step 462, sub-module 460 or another sub-moduleperforms an optional step in which the reliability, throughput, numberof hops, or a combination of one or more of reliability, throughput andnumber of hops for each of the possible paths is determined orcalculated. This determination or calculation can be used inidentification of potentially acceptable paths as described below withrespect to sub-module 465 and step 467 to designate one or more pathsthat meet multiple constraints.

Next, at step 467, the potentially acceptable path identificationsub-module 465 identifies potentially acceptable paths by comparison ofthe calculated end-to-end delay determined at step 462 with the maximumallowable end-to-end delay specified in the set of delay rules 420(column 424). The set of delay rules 420 includes, in certainembodiments, specified maximum allowable end-to-end delay 424 per usageclass 422, denoted as ψ(i,max). Paths are identified as potentiallyacceptable if Equation (9b) set forth above is satisfied.

In the method of the module 410, even though certain paths can beidentified as potentially acceptable at step 467, these potentiallyacceptable paths will not be assigned to the routing table 190 if anyone of the tier delays exceeds the maximum allowable tier delayψ(j,i,max). Therefore, the tier delay calculation sub-module 470 andlink identification sub-module 475 are incorporated to ensure that thedelay at each tier meets the constraints. In particular, the tier delaycalculation sub-module 470 calculates at step 472 the tier delay foreach of the links or set of links in tier j for the possible pathsdetermined in step 152. These calculations can be based upon networkstatistics, for instance, as described with respect to FIG. 10(reference numeral 364). For example, each transmitted frame includes atimestamp with the time at which frame processing commences at thesource; when the frame is transmitted from the last node in the giventier, a transmission timestamp is incorporated, and the tier delay canbe calculated based on all frame or packet processing time andtransmission time at each node in the path in tier j.

In certain embodiments, in addition to calculating the tier delay ofeach of the possible paths at step 472, sub-module 470 or anothersub-module performs an optional step in which the reliability,throughput, number of hops, or a combination of one or more ofreliability, throughput and number of hops for each of the possiblepaths is determined or calculated, as described with respect to FIG. 16B(reference numeral 363).

Next, at step 477, the link identification sub-module 475 identifiesacceptable links or sets of links by comparison of the calculated tierdelay with the maximum allowable tier delay specified in the set ofmaximum allowable tier delay rules 420. A link or a set of links isidentified as acceptable if Equation (9a) set forth above is satisfied.The steps 472 and 477 are repeated for each tier j within a path, orunless a calculated tier delay exceeds the maximum allowable tier delay,at which point the path is discarded.

Finally, after Equation (9a) is satisfied for all tiers within a givenpath, the path assignment sub-module 480 assigns at step 482 theacceptable paths to the routing table 190. In additional embodiments ofthe present invention, at step 482, the path assignment sub-module 480also considers additional constraints in assigning paths to the pathrouting table 190, including reliability (e.g., following the module 110described with respect to FIGS. 14A and 14B), throughput, number ofhops, or a combination of one or more of reliability, throughput andnumber of hops, as indicated by step 383 in FIG. 16B.

In addition, in still further embodiments of the present invention, thepath assignment step 482 is iterative, wherein, based upon networkstatistics related to one or more of determined reliability, calculatedthroughput, number of hops and calculated tier delay, certain paths arediscarded and replaced with additional paths. The iterative nature ofthe delay module 410 allows the system and method to be adaptive tocontinuously maintain optimal network traffic flow, and is comprehendedin FIG. 17B with a dashed connector between steps 462 and 482.

FIG. 17C is a flow process diagram illustrating the operation of anembodiment of a delay minimization module 410′ adapted to prepare arouting table 190′ in a system including FNSs. A path determinationsub-module 150 determines at step 152′ possible paths between a selectedsource-destination pair. Step 152′ includes the additional constraints(as compared to step 152 of tier delay minimization module 410)described with respect to the route optimization module 110′, i.e., thatthe paths determination for each source-destination pair requirespassage through the anchor packet selection device for N neighboringFNSs

The result of execution of the tier delay minimization module 310′ isthe creation of the routing table 190′ as shown in FIG. 14D or 15D.

In certain embodiments of the present invention, certain paths havingwired connectivity are selected by the delay minimization module 410′ asat least one of the assigned paths for a source-destination pair for agive usage class, presuming that such paths have a delay that is lessthan that of paths that are entirely or substantially wireless. If morethan one hardwired path is available, they will both be used as assignedpaths and/or alternative paths. In further embodiments, for eachsource-destination pair, at least one wireless path is selected as anassigned or alternate path in the event that a hardwired link to the CCRis disabled, due to an unexpected failure or an anticipateddisconnection (e.g., for service or maintenance). Furthermore, ifmultiple paths are required to meet a usage class requirement, inpreferred embodiments paths are selected for routing table 190′ thatpass through different FNSs.

In additional embodiments as discussed above, the maximum allowablethroughput for a given link η(L(x,y),max) is considered in the selectionof the minimum number of independent paths N_(i) ^(opt) and/or theassignment of particular paths for a source-destination pair such thatthe following condition is satisfied:

η(L(x,y))≦η(L(x,y),max) for all y  (10).

In the event that the minimum number of independent paths N_(i) ^(opt)or the combination of the minimum number of independent paths N_(i)^(opt) and the allowed number of alternative paths cannot be assigned,one or more of the following can be implemented until the constraintsare met: (1) add another path, e.g., a set of WED, WID, MWID, MWID-JB,WGD, MWGD and/or MWGD-JB, to boost reliability, throughput or minimizedelay; (2) improve the reliability of the weakest link throughredundancy; and/or (3) use other RF channels and/or hopping patterns.

In still further embodiments of the present invention, based on thetraffic distribution and throughput, the number of channels per selectedpaths is determined to ensure that the maximum allowable tier delayψ(i,j,max) and η(L(x,y),max) are both satisfied. Paths with ψ(i,j,x)that exceed the maximum allowable tier delay ψ(i,j,max) or theend-to-end ψ(i,max) will either (1) be replaced with other paths, or (2)amended with multiple channels per path, in order to meet processcontrol system usage class requirements.

In accordance with conventional data frame architecture that is wellknown to those skilled in the art, each frame is supplied with a digitindicating whether it is an original transmission or a retransmittedframe. In accordance with certain embodiments of the present invention,the conventional data frame architecture is modified to reflecting itsusage class level. A usage class digit (UCD) is added in the routingtable for each source-destination pair to be utilized during the routingof a frame. This UCD is utilized in data frame transmission so thatframes are dropped if the frame usage class is greater than the UCD.That is, the system will route a frame only when the frame usage classis less than or equal to the UCD. In certain embodiments, forretransmitted frames, the process will allow passing the retried framesthrough the assigned and alternate paths irrespective of the UCD.

Table 3 below is a partial representation of a routing table betweencertain pairs of WIDs and WGDs, MWIDs and MWGDs, WIDs and MWGDs, orMWIDs and WGDs, which includes an indication of a UCD for the depictedpairs. Note that the pairs can be direct links or links withintermediate hops. For example, path 1 is a path between source address4E22 and destination address 22A4, and is an assigned path for frameswith a UCD of 3, whereby an initially transmitted frame with usage class0, 1, 2 or 3 will be passed, but an initially transmitted frame with ausage class of 4 or 5 will not be passed. Path 2 is an alternative pathbetween the same source-destination pair with a UCD of 5 or lower,whereby retransmitted frames of all classes will be passed through thepath. Path 3 is an alternate path between the 4B78 and 22A4source-destination address pair for all usage classes, i.e., allretransmitted frames will pass. Path 4 is an assigned path between 4E22and 22D9 for all usage classes. Path 5 is an alternate path between 4EAAand 22D9 for class 0, 1 and 2 only.

TABLE 3 (Part of the) Routing table Source Dest. Address Address WID/WGD/ Path MWID MWGD UCD Path Type 1 4E22 22A4 3 AS 2 4E22 22A4 5 AL 34B78 22A4 5 AL 4 4E22 22D9 5 AS 5 4EAA 22D9 2 AL — — — — — AS = AssignedPath AL = Alternate Path

The method and system of the present invention includes dynamicadjustment of routing to allow assigned and alternative paths to passtraffic irrespective of the usage class when either of the followingevents occur: (a) when a timeout occurs, either due to a violation ofthe maximum allowable delay (tier and/or end-to-end) or because anacknowledge message is not received, the assigned and alternate pathsfor the source-destination pair (where the timeout occurs) will allowall frames to pass irrespective of the usage class; (b) when the frameerror probability for a link within an assigned path exceeds a specifiedthreshold, all source-destination pairs with an assigned path throughthis link allows the assigned and alternate paths to pass all traffic. Amessage for adjustment of the routing table 190 or 190′ can be initiatedby the master WGD and/or the device that executed the route optimizationmodule 110. The adjustment of the routing table can be effective for apreset time duration, or until a second message is received requestingreversion to normal routing settings.

In additional embodiments of the present invention, a combination of theabove-described constraints is implemented to optimize and select routesfor a wireless process control and/or automation network. For eachparticular pair of source and destination, N_(P) is minimized such thatEquation (8) is satisfied for all i, with the additional conditions thatEquations (2), (6), (9a) and (10) are satisfied. If any of Equations(8), (2), (6), (9a) and (10) are not satisfied, than:

a. another path, i.e., a set of WED, WID, MWID, MWID-JB, WGD, MWGDand/or MWGD-JB, can be added to boost reliability, throughput orminimize delay;

b. the reliability of the weakest link can be improved throughredundancy;

c. other radio frequency channels and/or hopping patterns can be used;or

d. any combination of (a), (b) and (c) can be implemented.

The process is repeated for each source-destination pair in the wirelessprocess control and/or automation network, or each source-destinationpair in the wireless process control and/or automation network for whichoptimization according to the present invention is desired.

The above route optimization module described with respect to FIGS.14A-14C, optionally including the additional steps or sub-modules, canbe implemented with respect to the entire network or certainsource-destination pairs. In embodiments in which the path optimizationprocess is implemented for the entire network, the above process,optionally including the additional steps or embodiments, is repeatedfor each source-destination pair in the system. In embodiments in whichthe path optimization process is implemented for certain selectedsource-destination pairs, the above process, optionally including theadditional steps or embodiments, is repeated for the source-destinationpairs to be optimized. To prevent channel congestion with respect topairs that are not optimized, routing rules can be implemented thatprioritize the selected source-destination pairs through the assignedpaths, or through the assigned paths and alternate paths in embodimentsin which alternate paths are provided. In further embodiments, theassigned paths, or the assigned paths and alternate paths in embodimentsin which alternate paths are provided, can be reserved exclusively forthe source-destination pairs selected for optimization according to themethod and system of the present invention.

In accordance with the present invention, once the routing table isestablished that assigns a minimum number of reliable paths, and incertain embodiments alternate paths, between a source-destination pairfor a given usage class, frames for retransmission are selected based onthe routing table. When a packet is transmitted from a particular sourcewithin a given usage class, when this packet reaches any device, e.g.,WID, WGD, MWID or MWGD in the network, the following decisions will bemade for appropriate retransmission:

-   -   If the device is within the assigned paths for a particular        source and destination pair usage class, this packet will be        transmitted to the next device(s) in the path(s);    -   If this device is within the alternative paths for a particular        source and destination pair usage class and there are no        exceptions, this packet will be dropped (i.e. will not be        transmitted to the next device(s) in the path(s));    -   If this device is not within the assigned/alternative paths for        a particular source and destination pair usage class, this        packet will be dropped (i.e. will not be transmitted to the next        device(s) in the path(s)).

Referring to FIG. 18, an overview 1100 of steps involved in executingthe hybrid system including integrating existing JBs, incorporating newMWID(s) and MWGD(s), defining the FNS(s), and setting the anchor packetselection device for each FNS is shown. The steps are carried outgenerally in accordance with the specific modules described herein.

Suitable JBs are determined at step 1101 for wired/wireless integration.The locations of new MWID(s) and MWGD(s) is determined at step 1102.Required interconnectivity changes are determined for wired/wirelessintegration at step 1103. The number and size of FNS(s) are determinedat step 1104. The initial anchor MWID(s) or MWGD(s) for eachsource-destination pair is determined at step 1105. The total number ofpaths for a source-destination pairs per usage class g is determined atstep 1106. A counter h is set at step 1107. At step 1108 a, a set ofpaths is determined for the h^(th) source-destination pair per usageclass, subject to the joint constraints inputted at step 1108 b,including maximum tier delay, maximum end-to-end delay, maximumthroughput, minimum link reliability level, required minimum reliabilityper usage class, MWID CPU maximum usage level, and the maximum number oflinks per path. At query step 1009, it is determined whether the set ofpaths meet all of the constraints. If not, improvements are identifiedat step 1110, including adding additional MWID(s) and/or MWGD(s), RFengineering, adding additional FNS(s), or upgrading equipment. If theconstraints are met in query step 1009, h is incremented by 1. At querystep 1112, it is determined whether h=g. If not, the process returns tostep 1108 a. If query step 1112 determines that h=g, at step 1113, theset of paths is assigned for the source-destination pair per usageclass, and the routing table is populated. The process repeats for eachsource-destination pair per usage class. At query step 1114, which canbe continuous or interim, it is determined whether there is any changein traffic loading, traffic distribution, or performance level, whetherthere is external interference, or whether there are hardware additions.If so, the process returns to step 1106.

For the purpose of demonstrating a wireless process control system usingthe optimization process and system of the present invention, referenceis made to the portion of an ISA-SP100 network shown in FIG. 19. Theportion depicted includes a single source-destination pair with multiplepaths. Each wireless link has a maximum capacity of 250 kbps, and aneffective achievable throughput of 100 kbps, since the maximumachievable throughput is typically in the range of 40% of link capacityfor CSMA-CA protocols and the like. The links' frame error rate profilesare given in Table 4, which also provides the existing levels ofthroughput per link. The process control equipment at WID L13 is assumedto generate 60 kbps when commissioned to the network, where 40 kbps isthe traffic going to the CCR (uplink) and 20 kbps is the traffic comingfrom the CCR to L13 (downlink).

Frame retransmission rates are assumed to be below 1% for all classes ofservice. It should be noted that these FER values will depend on thespecifics of the underlying physical layer, e.g., type of digitalmodulation and error control coding, radio channel path loss and fading,co-channel interference, etc. For illustration, typical FER values areassumed.

In Table 5, the required FERs per class are listed, and a typicaltraffic mix across the different classes of service is represented bythe percentage of frames belonging to Class 0, 1, 2, 3, 4 and 5. Inaddition, assumed limits for total end-to-end delay and per-tier delayare specified. In general, delay values will be related to the trafficloading and queuing/priority mechanisms. Actual delay values per linkcan be obtained empirically from message timestamps. Depending on thenumber of hops that a given frame has to make, the accrued delay can becomputed, which are accounted for in the optimization system and methodof the present invention to provide a certain end-to-end delay.

TABLE 4 η(L(x, y)) Source Destination Link FER (kbps) L13 L23 1.00E−05 0L13 L24 1.00E−06 0 L13 L25 5.00E−07 0 L13 L26 1.00E−07 0 L23 L325.00E−04 60 L24 L32 5.00E−06 30 L25 L32 5.00E−04 70 L26 L32 5.00E−03 90

TABLE 5 Maximum Allowable FER Traffic Mix End-to-End Tier 1 Tier 2 Tier3 Class Φ_(c)(i) D_(i) ψ(i, max) ψ(i, 1, max) ψ(i, 2, max) ψ(i, 3, max)0 1.00E−08 0% 0.3 sec 0.1 sec 0.1 sec 0.1 sec 1 1.00E−08 8% 0.5 sec 0.2sec 0.2 sec 0.1 sec 2 1.00E−07 10% 0.5 sec 0.2 sec 0.2 sec 0.1 sec 31.00E−06 12%   1 sec 0.4 sec 0.3 sec 0.3 sec 4 1.00E−05 35%   5 sec   2sec   2 sec   1 sec 5 1.00E−05 35%   5 sec   2 sec   2 sec   1 sec

Applying the given data into the process simulation model, the paths'frame error probabilities are calculated as shown in Table 6. The frameerror probabilities when transmitting frames over multiple independentpaths are then calculated as in Table 7. Based on the optimized routingmethod and system of the present invention, the assigned and alternatingpaths are given in Table 8. For the purpose of the present example, nomore than 2 paths are assigned.

Table 9 provides the resulting links' throughputs following the pathassignment of Table 8. Since the throughput of L26-L32 exceeds 100 kbps,a second RF channel is provided to support this traffic.

TABLE 6 Path Path Designation Φ(L(x, y)) L13-L23-L32 A 5.10E−04L13-L24-L32 B 6.00E−06 L13-L25-L32 C 5.00E−04 L13-L26-L32 D 5.00E−03

TABLE 7 Associated FER with Selected Paths x Φ(x) x Φ(x) A 5.10E−04 B &C 3.00E−09 B 6.00E−06 B & D 3.00E−08 C 5.00E−04 C & D 2.50E−06 D5.00E−03 A & B & C 1.53E−12 A & B 3.06E−09 A & B & D 1.53E−11 A & C2.55E−07 B & C & D 1.50E−11 A & D 2.55E−06 A & B & C & D 7.66E−15

TABLE 8 Assigned Alternate Class path path 0 A & B C & D 1 A & B C & D 2A & B C & D 3 A & B C & D 4 B A & C 5 B A & C

TABLE 9 Link Throughput Throughput Source Destination (kbps) L13 L23 46L13 L24 60 L13 L25 40 L13 L25 40 L23 L32 92 L24 L32 90 L25 L32 90 L26L32 110

The “normalized” spectrum usage (counted per RF channel use) can beestimated by taking into account the total number of RF channeloccupancies for the end-to-end connection. This can be calculated asfollows:

$\begin{matrix}{U = {\sum\limits_{i}^{\;}\; {D_{i}N_{i}}}} & (11)\end{matrix}$

where D_(i) represents the traffic distribution percentage for class i,and N_(i) is the number RF channels occupied per class. This expressionapplies to the standard (i.e., non-optimized) operation procedure.However, with the optimization algorithm of this invention, thenormalized spectrum usage becomes:

$\begin{matrix}{U = {{\sum\limits_{i}^{\;}\; {D_{i}N_{i}^{opt}}} + {P_{ret}{\sum\limits_{i}^{\;}\; {D_{i}\left( {N_{i}^{opt} + 2} \right)}}}}} & (12)\end{matrix}$

where P_(ret) is the average retransmitted probability in the system. Byapplying these formulas for the specific parameters used in thisexample, under standard non-optimized operation the following result forspectrum utilization is attained:

U=1+4*(0%+8%+10%+12%+35%+35%)=5,

since there is one RF transmission from L13 to a WID, and four separateRF transmissions going from WID to WGD. On the other hand, thenormalized spectrum usage is obtained as follows for the case of theprocess optimization of this invention:

U=[1+2*(8%+10%+12%)+1*(35%+35%)]+0.01*4[(8%+10%+12%)+3*(35%+35%)]=2.4where 1% retransmission probability is assumed.

The ratio of 5/2.4≅2 indicates that double the spectrum would berequired if the process optimization of this invention is not followed.Notably, these savings in spectrum consumption do not preclude meetingthe minimum usage class requirements.

This optimization procedure can also significantly reduce powerconsumption for the nodes. Battery power usage is directly proportionalto the number of transmitted and received frames, and is notsignificantly impacted by other processing activities such asencryption, authentication, heartbeat signal, and the like. FIGS. 20Aand 20B show the normalized power usage (which is proportional to thenumber of frames transmitted and received) from L13 to L32, with andwithout the optimization scheme. Note that for the purpose of FIGS. 20Aand 20B, a single transmission consists of a frame sent from L13 to L32and the acknowledgement frames sent from L32 to L13.

FIG. 20A indicates that the number of received frames for the four WIDsremains the same with and without the optimization scheme, whereas thenumber of transmitted frames drops from 8 to 2.3 frames when theoptimization scheme is implemented. FIG. 20B demonstrates that thenumber of frames received by the WED and WGD drop from 8 to 2.6 for asingle transmission, while the number of transmitted frames remainunchanged. Thus, the implementation of the optimization scheme extendsbattery lifecycle by 55% (16/10.3) for WIDs, and by 117% (10/4.6) forWEDs.

FIGS. 21A and 21B are schematic explanatory diagrams of two possibleconfigurations of FNSs 820. Segmenting the wireless network intoexcessive FNSs will not yield a high performance gain, while segmentingthe plant wireless network into too few FNSs will result in decrease inpath redundancy, thus in the event of a point of failure, a reduction ofpacket reliability/availability can occur.

The selection of the FNS members and size is dynamic. When one or morenew devices (e.g., field end devices, having wired or wirelessconnectivity, WIDs, MWIDs, WGD and/or MWGDs) are added, devices arerearranged, or devices are removed, the FNSs size and/or number isdynamically altered if necessary to achieve the requisite packet routingand/or path requirement constraints. An FNS architecture module isexecuted or re-executed to account for the removed, added or rearrangeddevices. For instance, an FNS that encompasses and borders additional orrearranged devices affects the size of the FNS, e.g., the FNS becomeslarger, or requires dividing the FNS into multiple FNSs. Accordingly,the selection of the FNS members and size includes (but is notnecessarily limited to) the following considerations:

geographical area/plant environment;

maximum allowable delay;

whether one or more devices, including field end devices, having wiredor wireless connectivity, WIDs, MWIDs, WGD and/or MWGDs, are added,subtracted or rearranged;

network loading (e.g., the number of destination-source pairs);

diversity requirements (support of multiple paths) to meet reliabilityrequirements; and

availability of redundant links to the CCR.

Given the above factors, a practical FNS size limit can be provisionedas follows:

with 1 MWID-JB connection to a MWGD-JB, the number of MWID within an FNScan be between 1 to 5;

with 2 MWID-JB connections to a MWGD-JB, the number of MWID within anFNS can be between 1 to 10;

with 1 MWID-JB connection to the master WGD or directly to CCR, thenumber of MWID within an FNS can be between 1 to 5; and

with 2 MWID-JB connections to the master WGD or directly to CCR, thenumber of MWID within an FNS can be between 1 to 10.

In addition, within an FNS, a MWID is preferably selected as being theinterface for wired connectivity to the CCR, e.g., as a member of anMWID-JB set. Considerations include physical proximity to the CCR,minimizing the number of transmissions within the FNS is achieved, andwhether a JB exists in the plant that is proximate to that particularMWID candidate. Similar considerations are used in selecting theinterface for an FNS in the WGD tier.

For a particular source-destination pair, one particular MWID within anFNS is tagged as the anchor packet selection device for all transmittedpackets from a particular source. The one packet with the highestquality index is selected by the anchor forwarded, potentially overmultiple links or paths, through the MWID-JB and then through MWGD tothe Master Gateway then to CCR.

The method of selecting the anchor MWID to perform the selectingfunction for a particular source-destination pair includes: A) selectingthe nearest FNS to the source (nearest to the WID or MWID in the FNS);B) selecting the MWID-JB as the anchor packet selection MWID, and ifthat MWID-JB's CPU is fully loaded, then selecting the MWID within thecenter of FNS; C) if the selected MWID within the center of FNS is fullyloaded, in terms of path throughput or packet selection functions, thenselecting the nearest to center MWID, and so forth; D) if all MWIDswithin an FNS are fully loaded, then selecting a different FNS; E) if asecond path is needed of if a second FNS is required for that particularsource-destination pair, then repeat steps A-D for selecting the anchorMWID for the second FNS. When we have two FNSs are required for aparticular source-destination pair, anchor MWIDs are need in each FNS.

In the forward direction, for a particular source-destination pair, oneparticular MWID within an FNS is tagged as the anchor packet selectiondevice for all transmitted packets from a particular source, and the onepacket with the highest quality index is selected and forwarded(potentially over multiple links or paths) through the MWID-JB, throughMWGD to the Master Gateway, and ultimately to CCR. The selected packetwill be forwarded and erroneous packets will be discarded at an earlystage. This is in contrast to prior art techniques, in which erroneouspacket(s) continue to propagate into the network (ineffectivelyutilizing the network resources, such as energy, spectrum, CPU power,and the like) and are dropped at master WGD, or multiple copies of thepacket are unnecessarily propagated through the network to reach thedestination (whereby the destination must determine which packet is tobe used).

In the reverse direction, the anchor MWID within an FNSsource-destination pair receives the packet from the CCR. Possiblesequences of packet transmission from CCR to WED include (but are notlimited to):

CCR to the master WGD to a MWGD-JB to a MWGD to a MWID to a MWID to thefield device (WED);

CCR to the master WGD to a MWGD to a MWID-JB to a MWID to the fielddevice (WED),

CCR to the master WGD to a MWGD-JB to a MWGD to a MWID-JB to a MWID to aWID to the field device (WED), or

CCR to the master WGD to a MWGD-JB to a MWID to the field device (WED).

The above sequences can be reversed to obtain the sequence oftransmission from the WED to the CCR.

If a packet belongs to particular source-destination pair and proceedsthrough two different FNSs, each set will have an anchor packetselection MWID for that pair source and destination. In addition, ananchor MWGD or MWGD-JB is used to provide the selection between the tworeceived packets from MWID sets.

Two concurrent schemes can be used to select the packet with the highestquality. A low density parity check (LDPC) can be implemented to verifythe quality of each packet, and majority logic combining can also beused. As an example, of packet selection, if two packets are receivedfrom different paths with different quality checks, the one with highestquality check is selected. If three packets are received from differentpaths but two are exactly in terms of information bits and/or paritycheck, one of these two packets will be selected.

The packet selection function for an FNS will be distributed (loadbalanced) among the various MWIDs within a given FNS to handle all pairsof source-destination paths. This can be implemented automaticallythrough the master WGD (e.g., using an operation similar to the pathselection sub-module 150) or determined manually by a plant operator.

The method and system of the present invention have been described aboveand in the attached drawings; however, modifications will be apparent tothose of ordinary skill in the art and the scope of protection for theinvention is to be defined by the claims that follow. In addition, whilecertain implementations of the present invention have been describedwith respect to the ISA-SP100 protocol, the present invention can alsobe implemented within other wireless process control and/or automationprotocols including but not limited to the HART® protocol.

We claim:
 1. A process control and/or automation network for acommercial or industrial processing facility, the network comprising: adistributed control system in a central control room within thefacility; a first tier comprising a plurality of wireless end devicesreceiving instructions from and/or providing data to the distributedcontrol system, the instructions and/or data in the form of packets,each wireless end device being associated with one or more meters,remote terminal units, diagnostic devices, pumps, valves, sensors, ortank level measuring devices; a second tier comprising a plurality ofwireless routers each including a memory that stores a routing table anda processor that routes packets; and a third tier comprising a masterwireless gateway device operably connected to receive packets from andtransmit packets to the distributed control system; wherein theprocessor of each of the plurality of wireless routers routes packetsacross the three tiers between the plurality of end devices and thewireless gateway devices based on the stored routing table.
 2. Theprocess control and/or automation network as in claim 1, furthercomprising a plurality of field network sets each containing one or moreof the plurality of wireless routers or one or more wireless gatewaydevices.
 3. The process control and/or automation network as in claim 2,further comprising at least one marshalling cabinet and at least onejunction box, the at least one junction box within one of the fieldnetwork sets and wired to the marshalling cabinet for communication. 4.The process control and/or automation network as in claim 3, furthercomprising a junction box router in wired communication between thejunction box and the marshalling cabinet and in wired communication withthe master gateway device.
 5. The process control and/or automationnetwork as in claim 4, wherein a wireless router in the field networkset containing the junction box is configured for wired communicationand is wired to the junction box.
 6. The process control and/orautomation network as in claim 5, wherein the wireless router that iswired to the junction box is a wireless intermediate device.
 7. Theprocess control and/or automation network as in claim 5, wherein thewireless router that is wired to the junction box is a wireless gatewaydevice.
 8. The process control and/or automation network as in claim 1,wherein the routing table stored in memory of the wireless routerspecifies, for each wireless end device, a predetermined number ofassigned paths from the wireless end device to the master gateway deviceper usage class, the wireless router further storing a frame selectionmodule executable by the processor of the wireless router that, uponreceipt of a packet to or from a wireless end device, permitstransmission of the packet along the assigned path if the router iswithin that particular assigned path, or drops the packet if thewireless router is not in the assigned path.
 9. The process controland/or automation network as in claim 1, wherein the routing tablestored in memory of the wireless router specifies, for each wireless enddevice, a predetermined number of assigned and alternate paths from thewireless end device to the master gateway device per usage class; thewireless router further storing a frame selection module executable bythe processor of the wireless router that, upon receipt of a packet toor from a wireless end device, permits transmission of the packet alongthe assigned path if the router is within that particular assigned path,or permits transmission of the packet along the alternate path if therouter is within that particular alternate path and there exists anexception in the network that requires use of the alternate path, ordrops the packet if the wireless router is not in the assigned oralternate path.
 10. The process control and/or automation network asclaim 2, wherein at least one of the field network sets has at least onejunction box, and wherein at least one of the wireless routers isconfigured for wired communication and wired to a junction box, andwherein one of the wireless routers that is wired to a junction box isdesignated as an anchor packet selection device through which alltraffic in that field network set is routed.
 11. The process controland/or automation network as in claim 10, wherein the routing tablestored in memory of the wireless router specifies, for each wireless enddevice, a predetermined number of assigned paths from the wireless enddevice to the master gateway device per usage class, the wireless routerfurther storing a frame selection module executable by the processor ofthe wireless router that, upon receipt of a packet to or from a wirelessend device, permits transmission of the packet along the assigned pathif the router is within that particular assigned path, or drops thepacket if the wireless router is not in the assigned path; wherein theanchor packet selection device of each network set and for each tierfurther includes a packet selection module executable by the processorof the anchor packet selection device to select a packet among pluralpackets of the same information with the highest quality forretransmission; and wherein the frame selection module receives the bestpacket from the packet selection module and transmits at least one copyof the best packet in the assigned paths toward the destination or thenext tier.
 12. The process control and/or automation network as in claim11, wherein the packet selection module implements a low density paritycheck.
 13. The process control and/or automation network as in claim 11,wherein the packet selection module implements a load balancing protocolto distribute traffic among various wireless routers in the fieldnetwork set.
 14. The process control and/or automation network as inclaim 11, wherein the packet selection module implements a low densityparity check and a load balancing protocol to distribute traffic amongvarious wireless routers in the field network set.
 15. The processcontrol and/or automation network as in claim 2, wherein at least someof the wireless routers in a field network set include a wireless routerwired to a junction box which contain stored in their memories fieldnetwork set information as to which wireless routers are wired tojunction boxes and their respective performance characteristics, thewireless routers having field network set information further comprisinga routing module that uses the field network set information todynamically route packets within the field network set.
 16. The processcontrol and/or automation network as in claim 2, wherein at least someof the wireless routers in a field network set include a wireless routerwired to a junction box, wherein field network sets including a wirelessrouter wired to a junction box are wired to the central control room.17. The process control and/or automation network as in claim 16,wherein the field network sets including a wireless router wired to ajunction box include a designated junction box that is wired to thedistributed control system in the central control room.
 18. The processcontrol and/or automation network as in claim 16, wherein the wiredconnection is through a marshalling cabinet.
 19. The process controland/or automation network as in claim 16, wherein the wired connectionis through a junction box router.
 20. The process control and/orautomation network as in claim 1, further comprising a plurality offield network sets spanning across multiple tiers, each field networkset containing one or more of the plurality of wireless routers and oneor more wireless gateway devices, wherein the routers and gatewaydevices of each field network set act as a single routing device toroute packets to routers and gateway devices external to the fieldnetwork set.
 21. The process control and/or automation network as inclaim 20, further comprising at least one marshalling cabinet and atleast one junction box, the at least one junction box within one of thefield network sets and wired to the marshalling cabinet forcommunication.
 22. The process control and/or automation network as inclaim 21, further comprising a junction box router in wiredcommunication between the junction box and the marshalling cabinet andin wired communication with the master gateway device.
 23. The processcontrol and/or automation network as in claim 22, wherein a wirelessrouter in the field network set containing the junction box isconfigured for wired communication and is wired to the junction box. 24.The process control and/or automation network as in claim 23, whereinthe wireless router that is wired to the junction box is a wirelessintermediate device.
 25. The process control and/or automation networkas in claim 5, wherein the wireless router that is wired to the junctionbox is a wireless gateway device.